The billionaire businessman will descend on Capitol Hill for a rally with Cruz early Wednesday afternoon, joining tea party leaders and several pro-Israel groups. Some House members are also expected to attend, while Congress debates the Iran resolution inside.
In his opinion piece, Trump said "it was amateur hour for those charged with striking this deal with Iran, demonstrating to the world, yet again, the total incompetence of our president and politicians."
Trump pledged that his presidency "will use all the tools of power available" to prevent Iran from gaining a nuclear weapon, though he added that he intends on "hopefully avoiding direct action."
Predicting that Iran wouldn't hold up its end of the bargain, Trump opposed the Iran deal soon after it was announced.
"You know Iranians are going to cheat," Trump told NBC News in July. "They're great negotiators and you know they're going to cheat."
Several conservative darlings will be joining Trump and Cruz, including radio host Glenn Beck and former vice presidential candidate Sarah Palin. Republican 2016 contender Jim Gilmore, Virginia's former governor, will also attend the rally.
Palin, who announced on Facebook that she would attend the rally, wrote: "Think about it - what the heck are we even doing 'negotiating' with an evil regime hellbent on destruction?"
"The whole premise of this thing is wrong," the former reality television star added. "It's a long haul to D.C. for the rally but well worth it to take a stand against this asinine deal the president caved on."
Presidential candidates opposing the deal aren't the only ones heading to Washington as congressional debate begins on the issue. Not far from the Capitol, Hillary Clinton voiced her support for the agreement in a speech Wednesday morning.