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Ted Cruz and Donald Trump will appear together at a rally on Iran

The two candidates have previously agreed on immigration policies

Washington CNN  — 

Presidential hopefuls Donald Trump and Ted Cruz are planning to rally together on the grounds of the Capitol to “call on members of Congress to defeat the catastrophic” Iran nuclear deal, Cruz’s campaign said Thursday.

The Texas senator said in a tweet that he was “glad that @realDonaldTrump accepted my invitation,” an invitation confirmed by event organizers.

Cruz’s announcement came a few hours after Trump announced in a speech in South Carolina that he expected to do an Iran event with Cruz, predicting it would draw a “tremendous crowd.”

The event on the West Lawn on Sept. 9 will show the alliance between Cruz and Trump in the most visible terms yet. The Texas senator has been one of only a few Republican presidential candidates to not criticize Trump, repeatedly declining for months to distance himself from his incendiary rhetoric or policy positions. Cruz has positioned himself in lockstep with the businessman most notably on Trump’s immigration platform, endorsing his push last week to end automatic birthright citizenship.

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But it is foreign policy, not immigration, that will bring the two side by side. The Iran deal – which Cruz has vowed to “rip to shreds” on his first day in office – will be the primary item on Congress’s agenda when it returns from its summer recess, but in contrast to Cruz, Trump has merely pledged to strictly “police” the contract.

“This ‘deal’ does not prevent Iran from getting nuclear weapons; it virtually guarantees it. Congress must reject this terrible deal,” said Jenny Beth Martin, the leader of Tea Party Patriots, one of three groups organizing the event.

The news of the joint event comes as some signs that the alliance may be tested. Trump said in South Carolina that he may have to unveil his first “hits” on Cruz if he “starts getting really close,” and in an interview with National Journal published Thursday, Cruz suggested that he too may distinguish himself from Trump as the campaign seasons change.

Earlier this month, Trump was asked about a Daily Beast report raising the possibility that he could be doing a joint event with Cruz. “We’re not,” he told reporters in New Hampshire.

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CNN’s Jeremy Diamond contributed to this report.