Republican presidential rivals Donald Trump and Ted Cruz are teaming up in opposition against President Barack Obama's proposed nuclear deal with Iran, with both candidates confirming Thursday that they will make a joint appearance at a rally on Capitol Hill in Washington, D.C.

Trump, the GOP front-runner by far, announced the event during a 45-minute speech in South Carolina on Thursday, reported The Associated Press.

"We are talking to Ted Cruz, who is a friend of mine and a good guy, about doing something very big over the next two weeks in Washington," the billionaire businessman said, reported The Washington Post. "It's essentially a protest against the totally incompetent deal that we're making with Iran."

Cruz's spokeswoman Catherine Frazier said the Texas senator invited Trump to join him at the Capitol "to call on members of Congress to defeat the catastrophic deal that the Obama administration has struck with the Islamic Republic of Iran."

The event will be co-sponsored by the Tea Party Patriots, the Center for Security Policy and the Zionist Organization of America, Frazier said.

Morton Klein, president of the Zionist Organization of America, said the rally is tentatively scheduled to take place Sept. 9, and welcomed Trump's involvement, reported Politico.

"Anybody who's in public life and opposed to the deal, it's useful to have them speak out and oppose this catastrophe. It's not a bad deal, it's a catastrophe. Every American should be freaking out about arming and funding the Hitler of the day," Klein said.

Trump and Cruz have forged an interesting alliance, with Cruz being one of the only Republicans in the race to avoid publicly criticizing the highly controversial real estate mogul, even after Trump's comments questioning Sen. John McCain's status as a war hero and comments about Mexican immigrants being rapists.

Other than opposing the Iran deal, the two have a few similar policy stances - both espouse anti-establishment ideals to populists frustrated with how Washington works, and both have made immigration central issues of their campaign, notes AP.

Last month, Cruz visited Trump in his New York office to build a rapport, and eventually win over some of Trump's supporters, according to Cruz spokesman Rick Tyler.

"We want to win over all the supporters of other candidates. [Trump] has the most voters that we hope to eventually win their support," he said, according to the Post.

Frazier said the timing of the event is not set in stone due to the campaigns and groups involved. "We are thankful for all their hard work on this effort and will have more details on time, date, and location as they are finalized," she said.

Congress is expected to begin debating the Iran deal when lawmakers return from summer recess Sept. 8. They have until Sept. 17 to approve or reject the deal.