(Adds briefing for full House of Representatives, paragraph 6)
By Patricia Zengerle and Steve Holland
WASHINGTON Dec 3 The White House said on Tuesday it opposes a fresh effort by some members of the U.S. Senate to impose new sanctions against Iran, even if the new restrictions would not take effect for months.
Some senators have been discussing the idea of imposing new sanctions on Iran that would kick in after six months or if Iran violated terms of an interim deal reached 10 days ago that attempts to contain its nuclear program.
"If we pass sanctions now, even with a deferred trigger which has been discussed, the Iranians, and likely our international partners, will see us as having negotiated in bad faith," White House spokesman Jay Carney told reporters.
Administration officials have been pushing lawmakers not to move ahead with a sanctions package, saying doing so risked alienating Tehran and other countries engaged in the talks by making Washington seem to be acting in bad faith.
But many lawmakers are skeptical about the agreement reached in Geneva between negotiators for Iran and the so-called P5+1 - the United States, China, Russia, Britain, France and Germany - and insist Washington should increase the pressure on Tehran by adding to sanctions.
Wendy Sherman, the U.S. under secretary of state for political affairs, who led the U.S. negotiating team in Geneva, was scheduled to hold a classified briefing on Iran for the entire House of Representatives on Wednesday morning.
The White House says a six-month window without new sanctions would allow negotiators to work on a comprehensive agreement to resolve the decade-old dispute over Iran's nuclear program, which has stirred fears of a new Middle East war.
But lawmakers believe it was tough sanctions pushed by Congress - not the White House - that brought Tehran to the table and see no reason not to spell out tough consequences if Iran does not comply with the interim deal.
"That way we're not negotiating in what-ifs," a Senate aide said.
Members of Congress, including many of President Barack Obama's fellow Democrats, are generally more hawkish on Iran than the administration, and influential pro-Israel lobbyists have been pressing lawmakers to keep to a tough line.
Carney said there are concerns in the Obama administration that any new sanctions imposed by Congress would serve to undermine the core architecture of the sanctions program.
"Passing any new sanctions right now would undermine a peaceful resolution to this issue," he said.
Iran rejects allegations that it has sought covertly to develop the capacity to produce nuclear weapons, saying it is enriching uranium solely for civilian purposes.
Congressional aides said it was too early to know whether an Iran sanctions package would be introduced as standalone legislation or as an amendment to a measure such as a defense authorization bill being considered by the Senate.
It also was not clear how far any legislation would go in the Senate, where Obama's fellow Democrats control a majority of votes.
(Reporting by Steve Holland; editing by Jackie Frank and Cynthia Osterman)