Washington (CNN) -- State Department spokeswoman Jen Psaki called Friday for the release of ousted Egyptian President Mohamed Morsy from detention, marking the first time the United States has made such a call.
Psaki said the detentions of Morsy and members of the Muslim Brotherhood were "politically motivated" and urged the military to let them go.
Morsy, the nation's first democratically elected president, was ousted on July 3 by the Egyptian military.
Tens of thousands of people rallied Friday in front of a Cairo mosque calling not only for his release, but for his restoration to the job of president. Morsy's supporters filled two avenues of the Nasr City neighborhood as far as the eye could see.
Fifty-one people died there Monday when protesters clashed with security forces, who opened fire.
Many of his supporters have vowed to risk their lives to see him back in power.
Those backing his overthrow were unpersuaded. Interim Prime Minister Hazem El-Beblawi was working to complete a new government by Monday, a state news agency said.
Turkey behind Morsy
The prime minister of Turkey, a close U.S. ally, agreed with the Brotherhood on Thursday, calling the coup that removed the Islamist president from power "illegitimate."
"Every military coup, regardless of its target, country and reason, is the murderer of the democracy, people and the future of the country," Recep Tayyip Erdogan said, according to the Anadolu state news agency.
Massive protests in Tahrir Square against Morsy did not make a coup legal, he said.
Erdogan heads an Islamic government and has faced off in street battles with secular protesters recently. His country's military has traditionally held the role of preserving the secular nature of Turkish democracy.
Saudi Arabia, U.S. talk
The Obama administration has not referred to Morsy's ouster through military might as a "coup." The use of the term could force the United States to terminate aid to Egypt's military.
A Pentagon source said Thursday that the White House planned to deliver four F-16 fighters to Egypt, but is reviewing its military aid arrangements.
President Barack Obama spoke by telephone with Saudi King Abdullah about the recent developments in Egypt.
"They agreed that the United States and Saudi Arabia have a shared interest in supporting Egypt's stability," according to a readout of their conversation.
"The president expressed his serious concern about the violence in Egypt and underscored the urgent need for an inclusive political process that will enable an early return to a democratically elected civilian government in Egypt."
CNN's Elise Labott, Yousuf Basil and Barbara Starr contributed to this report.