Iran's supreme leader, Ayatollah Ali Khamenei, criticized an open letter sent by 47 U.S. Republican Senators to Tehran about the ongoing negotiations on Iran's nuclear program, saying the move showed "disintegration" in U.S. politics.
The letter warns that the next U.S. president could revoke any deal Iran may reach with a group of six world powers (P5+1). Those talks are due to resume Sunday as the two sides seek an interim agreement by the end of the month.
Iranian state media quoted the supreme leader as saying he is concerned about what he called "backstabbing" in the negotiation process. He said that the international group, particularly the U.S., takes a harsher tone when the two sides get close to the end of the talks.
"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. This is the nature of their tricks and deceptions," the Mehr news agency quoted the Iranian leader as saying.
The clerical Supreme Leader said the letter was ''a sign of the decay of political ethics in the American system", and he described as laughable long-standing U.S. accusations of Iranian involvement in terrorism.
Khamenei has long been a conservative hardliner wary of any detente with the West but has backed the diplomacy pursued by Rouhani, who was elected by a landslide in 2013 promising steps to end Iran's economically crippling international isolation.
At the same time, Khamenei has not stopped speeches loaded with denunciations of the United States to reassure powerful hardliners in the clergy and security services, for whom anti-U.S. sentiment has been central to Iran's Islamic Revolution.
Iran has insisted it is not trying to build nuclear weapons. The United States, Britain, China, France, Russia and Germany are seeking assurances that the Iranian nuclear program is peaceful in exchange for lifting economic sanctions.
U.S. Secretary of State John Kerry said Wednesday the letter left him in "utter disbelief," and that Congress does not have the right to modify an agreement reached between the leaders of countries. He called the Republican letter irresponsible.
"No one is questioning anybody's right to dissent. But to write to the leaders in the middle of a negotiation.....and suggest they're going to give a constitutional lesson, which by the way is incorrect, is quite stunning," Kerry said.
Kerry told the Senate Foreign Relations Committee that the letter written by Arkansas freshman Senator Tom Cotton undermines U.S. foreign policy and ignores more than 200 years of history.
Some material for this report came from Reuters.