(CNN) -- Throughout much of the 1990s, U.N. weapons inspectors criss-crossed Iraq in search of Saddam Hussein's stocks of chemical weapons. It was a game of cat and mouse, as inspectors tried to reconcile what the Iraqi regime was telling them with conflicting intelligence from western governments.
In total, the inspectors of the U.N. Special Commission supervised the destruction of more than 40,000 chemical munitions, some 500,000 liters of chemical agents, 1.8 million liters of chemical precursors and delivery systems including ballistic missile warheads.
That experience may provide a glimpse of the obstacles to securing and removing or destroying Syria's massive stocks of the precursors that make chemical weapons. According to a new study by the International Institute for Counter-Terrorism in Israel, "Syria has accumulated since the 1980s a stockpile of approximately 1,000 tons of chemical weapons, stored in some 50 different sites."
Russian Foreign Minister Sergey Lavrov said Tuesday he was working on a concrete plan for removing Syria's chemical weapons. Last year the U.S. Defense Department estimated that it might take as many as 70,000 troops to secure Syria's chemical weapons stockpile. That admittedly involved intervening in a conflict -- as opposed to having permission to access sites -- but it provides an indication of the scale of the task.
Part of the problem is that Syria does not have one or even several facilities where its chemical agents are held. It has dozens.
"Syria's overall chemical weapons program is large, complex and geographically dispersed, with sites for storage, production, and preparation," James Clapper, the Director of National Intelligence, wrote in March this year.
The new IICT study echoes others that conclude there are five major production and research sites, mainly in the north, and the main research center is in Damascus. CNN correspondent Arwa Damon got close to the largest site -- at As-Safira near Aleppo -- last year. While rebels controlled the hinterland around it, the facility itself was well-protected. Syria's battle lines have shifted since then, and the country more resembles a patchwork of fiefdoms, complicating the task of making safe the chemical agents.
Among the many issues that need to be resolved if Syria's chemical weapons are to be eliminated:
Would the inspectors work under the auspices of the U.N.? How many would be needed?
U.N. cover seems to be essential as the only form of inspection acceptable to all sides. Syria and Russia would not accept western inspectors unless they were under a U.N. umbrella. The United States would never accept Russian control of the operation.
The U.N. also has a wealth of experience in deploying inspectors and testing their findings, largely thanks to the exhaustive operations of UNSCOM in Iraq. Both U.S. and Russian inspectors belonged to UNSCOM teams.
Experts say removing Syria's chemical agents will need a detailed and ambitious plan, requiring hundreds of inspectors and technicians. (By the time UNSCOM's work ended in Iraq with the inspectors' expulsion, more than 1,000 individuals from more than 40 countries had served on inspection teams.)
France has suggested that the Organisation for the Prohibition of Chemical Weapons, based in the Hague, should play an important role in Syria. In a statement Tuesday, the organization's director-general, Ahmet Uzumcu, noted that the Chemical Weapons Convention is "based on zero tolerance for chemical weapons."
"The OPCW ... stands ready to support international efforts that would strengthen it," he added. But its modus operandi is rather different from that of UNSCOM. A spokesman told CNN Tuesday that the organization does not go on "fishing expeditions" for material. Instead it expects a state to issue "a declaration that details all of the elements of their arsenal and their locations," which is then verified with on-site inspections.
The OPCW is not part of the United Nations but works with it closely under a 2001 agreement. It has already gained experience in Syria. The U.N. team that investigated the most recent chemical attack outside Damascus included nine OPCW experts and three from the World Health Organization. But the OPCW is already engaged in clearing up some of the Gadhafi regime's leftover chemical agents and still has several tons of mustard gas precursors to destroy in Libya.
Qualified chemical weapons inspectors and technicians are not a dime a dozen.
What sort of U.N. Security Council Resolution is needed to give the inspections real force?
French Foreign Minister Laurent Fabius said Tuesday that any U.N. Security Council resolution would have to threaten "extremely serious" consequences if Syria violated its conditions. Fabius said a Chapter VII Resolution -- which permits both military and non-military means to restore peace -- would be required. For his part, U.S. President Barack Obama said Monday that the United States would be asking: "Can we arrive at something that is enforceable and serious?"
For western governments, the risk is that the wording of any U.N. resolution would provide the Syrians with wiggle room to prevaricate or obstruct. For example, different interpretations of the meaning of a Security Council resolution soured Russia's relations with the West after the Libyan conflict broke out. Moscow agreed to a resolution permitting intervention on humanitarian grounds (to save Benghazi from a bloodbath), only to complain later that it had been twisted to bring about regime change. This time it is the United States, France and Britain that will be studying the language closely.
The French have drafted a resolution, but many revisions and much wrangling are likely before it goes to a vote. President Vladimir Putin of Russia has already laid down one marker. "All of this will only mean anything if the United States and other nations supporting it tell us that they're giving up their plan to use force against Syria," he said in an interview Tuesday.
In a Google + Hangout event Tuesday, U.S. Secretary of State John Kerry made it clear Washington believes the Assad regime controls access to sites where chemical weapons are held, "and so we believe they need to show us a completely verifiable, completely accountable, and ongoing verifiable process by which we know we have all of the weapons, access to all sites in question, unlimited access investigation."
But much of the chemical arsenal in Syria appears to be stored and developed at "dual-use" facilities, which the regime will want to protect from prying eyes. For example, the Centre d'Etude et Recherche Scientifique in Damascus develops chemical and biological agents, according to western experts. But it is also thought to be at the heart of other military and scientific research. In a report earlier this year, the Nuclear Threat Initiative, a non-proliferation group, described the CERS as "the best-equipped research center in Syria, possessing better technical capacity and equipment than the four Syrian universities."
Similarly, a site at Jamraya north of Damascus is thought to contain both chemical weapons and other programs.
How much of complex sites like these would be open to unfettered access?
Chemical weapons are often known as the "poor man's nuclear weapon" because they are relatively cheap to produce. This poses another problem. Fertilizer plants and oil refineries have been identified in academic studies as being linked to Assad's chemical weapons program. They also will need to be inspected.
How can the inspectors' movement be assured in the midst of a civil war?
For seven years the weapons inspectors of the U.N. Special Commission trawled through Iraq looking for chemical weapons at some 120 facilities. They had sweeping powers including "unrestricted freedom of movement without advance notice in Iraq;" the "right to unimpeded access to any site or facility for the purpose of the on-site inspection;" and the "right to request, receive, examine, and copy any record data, or information...relevant to" its work.
UNSCOM was dealing with a recalcitrant and obstructive regime that did its best to mislead the U.N., but at least they were not trying to work during a war.
In Syria, how difficult would it be for inspectors to cross from government to rebel-held areas? How difficult would it be for them to make "surprise" inspections to make sure chemical weapons were not being moved or hidden? It took months for terms to be reached before the most recent U.N. inspection team was admitted to Syria, and it was at first permitted access to just three sites (before the August 21 attack, after which the inspectors were allowed into the Damascus suburb where the incident took place.)
How current is intelligence about the nature and location of Syria's chemical weapons stocks?
Several of the sites where supplies for chemical weapons were allegedly held have been surrounded or seized by rebels. Had those supplies been removed to safer places? And how do inspectors get in to check? Is there one team working in rebel-held areas and another in parts held by the regime?
Are chemical weapons still stored mainly as precursors? Or has part of Syria's arsenal already been deployed (if not used) in short-range missiles or artillery shells? There have been some indications, according to U.S. sources, that the regime has consolidated its chemical weapons stockpile in fewer places to better safeguard it. Senior U.S. military officials have been saying since early this year that the Syrian government has been moving its stocks of sarin and mustard gas.
It is very difficult for outsiders, even Israel and the United States, to be sure of what the Syrian regime is doing and what its intentions are. Intercepts and satellite imagery offer clues, and Israel has already carried out bombing raids against convoys said to be carrying weapons to the Lebanese militia Hezbollah, an ally of the Assad regime. But U.S. officials acknowledge that it's hard to keep track of the hundreds of military sites in Syria
Hezbollah units are now established inside Syria and were involved in the summer battle for control of the town of Qusayr. So it's more than tracking the movement of trucks from known Syrian military facilities to areas along the Syrian-Lebanese border where Hezbollah is well-established.
But one Israeli specialist in chemical weapons says moving weaponized chemical agents around is far from easy.
"There are many ways to know it with monitoring," according to Ely Karmon, a senior research scholar at the IICT. He told CNN they are "difficult to transport, you need specialists to ensure they don't leak or explode along the way. And Hezbollah has no knowledge (of chemical weapons) so should they perhaps involve the Iranians or Syrian technicians?"
How can such a huge amount of material be safely moved out of a war zone?
Transporting hundreds of tons of chemicals through a country ravaged by war, where the rebels are a patchwork of militias and major routes are not under the government's control, is a huge logistical challenge. Convoys would need to be guarded, airports secured and/or border crossings secured. But who does the guarding? Syrian troops? Unlikely unless supervised by an international. U.S. troops? No one is floating that idea.
Alternatively, sites within Syria where chemical weapons precursors could be safely destroyed would have to be identified and guarded. This appears to be the preferred option of U.N. Secretary-General Ban Ki Moon.
"I am considering urging the Security Council to demand the immediate transfer of Syria's chemical weapons and chemical precursor stocks to places inside Syria where they can be safely stored and destroyed," he told reporters in New York Monday.
While chemical weapons stocks are relatively secure within army bases and research facilities, there is a greater risk once they are moved that they might fall into the wrong hands -- such as the jihadist groups active among Syria's rebels. However, Syria's chemical weapons are binary weapons, meaning that they are stored as separate ingredients that would have to be combined before becoming lethal. Using them would not be easy for militia groups.
What sort of time limit is feasible for such an operation, and who decides whether the Syrian regime is cooperating fully?
These are huge unanswered questions. The UNSCOM inspectors had to challenge Iraqi officials repeatedly with detailed documentary evidence that not all Iraq's chemical weapons had been declared. There were countless reports to the U.N. Security Council and 12 UNSC resolutions between 1991 and 1996 in support of its work.
Karmon estimates that the whole process in Syria could take three to four years and argues it would be impossible without a cease-fire, with the two sides retreating to allow inspectors to do their work. Given the stakes on the battlefield that Syria has become, that seems unlikely.
What's to stop the Assad regime starting over, especially if it sees a tactical advantage in using such weapons?
In 1989, then-CIA Director William Webster said Syria had begun producing chemical agents in the early 1980s. So Syria has some 30 years of experience in making chemical weapons and has built a network of suppliers all over the world. Defecting military officers have said that Iranian experts have helped develop Syria develop its arsenal and the missiles to deliver chemical weapons (despite Iran itself being targeted by chemical weapons during its war with Iraq.)
Starting a new chemical weapons program would not be technically difficult and could be done discreetly if on a limited scale. It might also be tempting for a regime whose conventional military strength is being eroded. Military analysts point out that Syria began developing chemical weapons capability decades ago to counter Israel's conventional military superiority. That superiority is even greater today than it was, and the Assad regime may one day again see possession of chemical weapons as critical to its survival.
CNN's Nick Paton Walsh and Jim Clancy contributed to this report.