GREENVILLE, S.C.—Donald Trump revealed Thursday that he’s been coordinating with Ted Cruz for a joint appearance at an event opposing the Iran deal in Washington.

“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 after a rally in South Carolina. “It’s essentially a protest against the totally incompetent deal that we’re making with Iran.”

A spokeswoman for the Texas senator said Cruz invited Trump to join him on the Capitol grounds “to call on members of Congress to defeat the catastrophic deal that the Obama Administration has struck with the Islamic Republic of Iran.”

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

Morton Klein, the president of the Zionist Organization of America, said the rally will take place Sept. 9.

More than any other Republican in the race, the Texas senator has steadfastly avoided publicly criticizing Trump, even after he shot to the top of the polls. As a litany of others trashed The Donald for his comments about Mexican immigrants and Sen. John McCain (R-Ariz.), Cruz carefully avoided any harsh words.

The Texan even traveled to Trump’s New York office last month to pay his respects, invite Trump to the U.S-Mexico border and build the rapport, hoping that he can eventually peel away some of the mogul’s support.

"We want to win over all the supporters of other candidates," Cruz spokesman Rick Tyler said earlier this month. “[Trump] has the most voters that we hope to eventually win their support."

The approach has begun to pay dividends, at least in the short term.

Earlier this year, Trump -- who previously demanded to see President Obama’s long-form birth certificate -- said Cruz’s 1970 birth in Canada, where his parents were working in the oil fields, was “a stumbling block” for his candidacy. Cruz’s mother is a native-born U.S. citizen.

Now Trump is sounding a much friendlier tune. During a 51-minute speech to a crowd of 1,400 supporters — after ripping into former Florida Gov. Jeb Bush, ex-Texas Gov. Rick Perry and South Carolina Sen. Lindsey Graham — Trump began praising Cruz.

“Sen. Cruz has been so nice to me,” he said. “Ted Cruz has been so great.”

A major Trump criticism of the Iran deal has been that the United States government did not do more to secure the release of prisoners, including The Washington Post’s Jason Rezaian and a Christian pastor.ent

Frazier said the timing of the event not locked in yet because of the groups and campaigns involved, so it’s too soon to say if it will happen next week.

“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.

Katie Zezima contributed to this story