"We will go from isolating Iran to isolating ourselves," she said in a speech at the University of Louisville, flanked by
The Senate, under McConnell's leadership, may consider new sanctions legislation by the end of the month, in the middle of a negotiating round that U.S. officials hope will yield a nuclear deal by March. Six world powers that have been in discussions with Iran failed to meet deadlines in July and November.
Power said the United States is unified with the five other countries in pressing Iran for an agreement to limit its nuclear activities. But if new sanctions were imposed, "Iran would be able to blame the U.S. for sabotaging the negotiations," she said.
New penalties would also undermine the current sanctions on Tehran, Power said. Countries that have supported worldwide reductions in purchases of Iranian oil would lose confidence in the collective effort and would ease their support for enforcement of its rules, she said.
"We will go from a position of collective strength to a position of individual weakness," she said.
The White House also said that President Obama assured Israeli Prime Minister Benjamin Netanyahu in a phone call Monday that the U.S. is committed to keeping Iran from developing a nuclear weapon. Obama told Netanyahu that Western negotiators are insisting that Iran, a rival of Israel in the Middle East, "verifiably assures the international community of the exclusively peaceful nature of its nuclear program."
Congressional advocates argue that Iran was first brought to the negotiating table by tough sanctions. Now, they say, more punishment is needed to persuade Tehran to agree to final compromises.
Meanwhile, an Iranian website with ties to conservatives in the government said Iran will not be offering new compromises when talks resume in Geneva on Wednesday.
The Iranian negotiating team is heading to Geneva "without any new mandate," the irannuc.ir website said. It quoted knowledgeable sources as saying that "the red and green lines of Iran have not changed."
Western officials have been hoping Iran would return to the table with a new willingness to compromise.
Staff writer Richter reported from Washington and special correspondent Mostaghim from Tehran.