Sen. Tom Cotton, R-Ark., criticized Iranian Foreign Minister Mohammed Javad Zarif’s “cowardly character” on Wednesday for studying in the United States during the Iran-Iraq War and challenged him to a debate on the U.S. Constitution. The first-term senator was the driving force behind a highly publicized open letter to the Iranian government signed by 47 Republicans that suggested the Republican-controlled Senate would shoot down any nuclear deal with Iran if lawmakers didn’t agree to its terms.

Cotton went after Zarif on Twitter after the latter reportedly “called out” Cotton during a speaking engagement at New York University. Zarif said that no matter what the Republican Senate or a future president thought of the pending deal, which must be finalized by June 30, the U.S. would be compelled to adhere to it. In short, the U.S. will roll back its economic sanctions in return for transparency and assurances regarding the peaceful nature of Iran's nuclear program. Iran will also have to significantly step down its nuclear capabilities if the deal goes through.

Zarif and Cotton both say the other does not understand the U.S. Constitution. Zarif maintains that Congress does not have to be consulted in regard to international treaties, but Cotton insists that Congress can shoot down any deal it doesn’t like. While Cotton is correct, historical practice in the U.S. is to leave international affairs to the White House.

The U.S. would “risk isolating themselves [sic] in the world if there is an agreement and they decide to break it,” Zarif said, when asked what Iran would do if a future U.S. government pulled out of the agreement and reinstated crippling economic sanctions on the Islamic republic. Zarif later called out Cotton directly:

“If we have an agreement on the 30th of June, within a few days after that, there will be a resolution before the UN Security Council under Article 41 of Chapter 7 which will be mandatory for all member states whether Senator Cotton likes it or not,” Zarif said, according to a statement from Cotton’s office.

Zarif also made it clear he does not “deal with Congress,” and that any internal political issues regarding the deal was “[Obama’s] problem.”

Cotton then sent Zarif a four-part message on Twitter:













Cotton added in a statement regarding Zarif’s comments that “[t]he repeated provocative statements made by members of the Iranian leadership demonstrate why Iran cannot be trusted and why the President’s decision to pursue this deal and grant dangerous concessions to Iran was ill-advised from the beginning.”

Zarif had not responded as of 7:15 p.m. EDT, but the career Iranian diplomat essentially shrugged off the March 9 letter signed by Cotton and his Republican colleagues, calling it “mostly a propaganda ploy” with no legal value.

"[I]t seems that the authors not only do not understand international law, but are not fully cognizant of the nuances of their own Constitution when it comes to presidential powers in the conduct of foreign policy,” Zarif said, regarding the letter.