Iran's Supreme Leader Ayatollah Ali Khamenei
Iran's Supreme Leader Ayatollah Ali KhameneiReuters

The letter written by Republican senators to Iran’s leadership has garnered quite a bit of criticism, with the latest coming on Thursday from Iran’s Supreme Leader, Ayatollah Ali Khamenei.

Speaking at a meeting with President Hassan Rouhani and senior clerics, Khamenei said the senators’ letter was a sign of the collapse of “political morality” in the United States, the Mehr news agency reported.

He added that according to international norms, governments are bound to their commitments and those rules cannot be breached with the change of government.

Khamenei further said he was worried about the letter because the United States was known for "backstabbing" and added that whenever negotiators made progress in nuclear talks with his country, the Americans became "harsher, tougher and coarser".

The letter, signed by 47 of the 54 Republican senators, warned Iran that any nuclear deal made with President Barack Obama, a Democrat, would last only as long as he remained in office and would be null and void after his term in office concludes.

"Of course I am worried, because the other side is known for opacity, deceit and backstabbing,” Khamenei said Thursday, according to Mehr.

"Every time we reach a stage where the end of the negotiations is in sight, the tone of the other side, specifically the Americans, becomes harsher, coarser and tougher. This is the nature of their tricks and deceptions," he charged.

The letter was fiercely criticized by Obama, who said on Monday, “I think it's somewhat ironic to see some members for Congress wanting to make common cause with the hard-liners in Iran. It's an unusual coalition.”

Vice President Joe Biden said in a statement on Monday night the letter was "expressly designed to undercut a sitting president in the midst of sensitive international negotiations" and was "beneath the dignity" of the Senate.

"This letter, in the guise of a constitutional lesson, ignores two centuries of precedent and threatens to undermine the ability of any future American president, whether Democrat or Republican, to negotiate with other nations on behalf of the United States," Biden wrote.

Former Secretary of State Hillary Clinton, a likely Democratic presidential candidate, lambasted the senators who wrote the letter and asked, "And one has to ask, what was the purpose of this letter?" "There appear to be two logical answers. Either these senators were trying to be helpful to the Iranians or harmful to the commander-in-chief in the midst of high-stakes international diplomacy. Either answer does discredit to the letters' signatories," she added.

Khamenei’s comments came after reports last week indicated that he was  urgently brought to a hospital in Tehran after several of his bodily systems had already failed. On Sunday there were rumors that the Supreme Leader had passed away but he quickly dispelled them by making a public appearance in Tehran.