Iran and the so-called P5-plus-1 -- the United States, Britain, Russia, France, China and Germany -- are working to consolidate gains made since an interim nuclear deal was reached last month in Geneva, Switzerland.
A U.S. Treasury Department decision to blacklist several companies for violating existing sanctions on Iran has frustrated authorities in Iran.
"The United States in practice showed that it is not trustworthy since the first day," Kazzem Seddiqi, a senior cleric, was quoted by the semiofficial Fars News Agency as saying during his sermon for Friday prayers.
Iran under the terms of the November agreement said it would curb its enrichment activity in exchange for relief from some economic sanctions.
U.S. Rep. Ed Royce, R-Calif., chairman of the House Foreign Affairs Committee, said Thursday additional sanctions could be "critical" in the drive to stop Iran from developing a nuclear weapon.
Iran says its nuclear program is for peaceful purposes.
White House spokesman Jay Carney told reporters Thursday new sanctions on Iran could undermine U.S. diplomacy as it relates to the Iranian negotiations.
President Barack Obama would veto any bill that would enforce new sanctions on Iran, he said.
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