By Patricia Zengerle and Arshad Mohammed
WASHINGTON (Reuters) - An initial agreement to curb Iran's nuclear program was "not perfect" but it bought time to try to secure a comprehensive deal, a top U.S. official said on Tuesday in response to sharp criticism from Congress.
Major world powers struck an agreement with Iran on November 24 to offer Tehran an estimated $7 billion in sanctions relief in return for steps to restrain Iranian atomic activities. The deal called for negotiation of a full agreement within a year.
Members of Congress have faulted the pact, arguing that it is unwise to ease sanctions before Iran takes aggressive action to rein in its nuclear program, which the United States, Israel and others suspect may aim to build bombs. Iran denies this.
"We see this as a first step so we don't consider the gaps that exist loopholes because this is not a final agreement," the lead U.S. negotiator with Iran, Under Secretary of State for Political Affairs Wendy Sherman, told lawmakers.
"This is not perfect but this does freeze and roll back their program in significant ways and give us time on the clock to in fact negotiate that comprehensive agreement," Sherman told the Senate Foreign Relations Committee.
U.S. lawmakers have some influence over Iran policy because of their ability to pass legislation imposing fresh sanctions on Iran, something U.S. President Barack Obama has opposed during the current negotiations and has threatened to veto.
An attempt to impose new sanctions on Iran has stalled in Congress and lawmakers are discussing whether to introduce a much weaker, non-binding resolution that expresses concern and calls for negotiators to set strict conditions in nuclear talks.
Senator Robert Menendez, a Democrat who chairs the Senate Foreign Relations Committee and also serves on the Senate Banking Committee that has primary jurisdiction on sanctions, made clear that he was not satisfied by the initial agreement.
"We have placed our incredibly effective international sanctions regime on the line without clearly defining the parameters of what we expect in a final agreement," he said.
"We need to guard against wanting a deal so much that we concede more than we gain. At the end of the day, Iran can no longer be a nuclear weapons threshold state," Menendez added.
Senator Bob Corker, the panel's senior Republican, suggested the interim deal was weak because it stops some Iranian nuclear activities but allows others to continue. He also said foreign companies are laying the groundwork to invest in Iran should sanctions ultimately melt away.
"There are people from all over the world who are clamoring to do business with Iran," he said.
Sherman said companies were visiting Iran in the hope there is a comprehensive deal although the U.S. believed no business deals were being struck yet.
"Although we don't want people to go because we think it does send the wrong message, if they do go it puts pressure perversely on the Rouhani administration," she said, suggesting that Iranian authorities could face some domestic backlash if rising expectations of such business deals are not realized.
Several lawmakers voiced concern about a proposed oil-for-goods swap between Russia and Iran. The United States has raised the deal with Tehran and Moscow and warned it could be subject to U.S. sanctions.
A Reuters report on January 10 revealed that Iran and Russia were negotiating a $1.5 billion per month oil-for-goods swap that would enable Iran to lift oil export substantially.
Sherman said the issue had been raised at "the highest level" to ensure it did not go ahead. "My own sense of this is, after a fair amount of clarity about this matter, that nothing will move forward at this time," she said.
(Reporting by Lesley Wroughton, Patricia Zengerle and Arshad Mohammed; Writing by Arshad Mohammed; Editing by Sandra Maler and Tom Brown)