TEHRAN, March 12 (UPI) -- Ayatollah Ali Khamenei, Iran's supreme leader, was critical of a letter sent by 47 U.S. Republican senators suggesting limitations to the value of an agreement on nuclear weapons.
The letter, which discouraged Iranian leaders from signing a treaty in the hopes of limiting Iran's progress in constructing nuclear weapons, also stated that the treaty could easily be undone after a new president is elected in the United States.
The sending of the letter has been denounced by the United States' chief negotiator, Secretary of State John Kerry, who said at a Senate hearing Wednesday, that the letter was factually incorrect and was a breach of protocol.
The New York Times referred to it "a blatant, dangerous effort to undercut the president on a grave national security issue by communicating directly with a foreign government."
Khamenei, in a Tehran speech Thursday, called the letter a late-game reversal of U.S. strategy designed to undermine a deal whose deadline is March 24.
"I'm concerned because the other side is into deception, trickery and backstabbing. This is part of their ploys and tricks," Khamenei said, according to the official Iranian Press TV.
The Iranian Mehr news agency said his comments included, "Of course I am worried. 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."
He called the letter ''a sign of the decay of political ethics in the American system."
Khamenei, although regarded as a conservative and hardliner suspicious of the West's motives, has backed the efforts of President Hassan Rouhani to negotiate a deal with the West to end economic sanctions and isolation.