Republican and Democratic U.S. senators on Sunday voiced skepticism about an interim nuclear deal reached with Iran but Congress looked likely to give President Barack Obama room to see if the agreement works.
The deal does not need to be ratified by Congress and Obama is using his executive power to temporarily suspend some existing U.S. sanctions on Iran.
Senators have been discussing for months imposing even tighter sanctions, which could anger Tehran and put Sunday's deal reached in Geneva in jeopardy.
But influential Democrats - who control the Senate - made clear that any new sanctions against Iran would include a six-month window before they took effect.
That would allow time to see if Iran is sticking by the pact, worked out between Tehran, the United States and other world powers.
"It is a choice between a pause or imminent war. I choose a verifiable pause," Senator Bill Nelson, a Democrat from Florida said.
Influential Democratic Senator Robert Menendez, who is known as a hawk on Iran, said forthcoming legislation would "provide for a six-month window to reach a final agreement before imposing new sanctions on Iran."
Menendez, who is chairman of the Senate Foreign Relations Committee and sits on the Senate Banking Committee, said the legislation would also make clear that the sanctions could kick in if talks toward a longer-term agreement falter or if Iran fails to live up to the interim agreement.
The agreement, reached after marathon talks in Switzerland, curbs the Iranian nuclear program in exchange for initial sanctions relief. Iran could access $1.5 billion from trade in gold and precious metals and could see the suspension of some sanctions on its automotive sector and a revival in its petrochemical exports.
While expressing concerns about the interim nuclear deal, even several Republican senators appeared willing on Sunday to allow time to judge its effectiveness.
Speaking on ABC television's "This Week," Republican Saxby Chambliss, vice chairman of the Senate Select Committee on Intelligence, said he believed a "strong movement" would build in the Senate for tighter sanctions.
But Chambliss said any bill would likely include a "time frame" before the actions would take effect.
"They've done this deal. And this can be done without the approval of Congress. So for the next six months, it looks like this deal is going to be in place," he said.
Senator Bob Corker, speaking on "Fox News Sunday," pledged to hold the Obama administration's "feet to the fire" to ensure that Tehran follows through on its obligations.
"My biggest concern is seeing follow-through here," said Corker, the top Republican on the Senate Foreign Relations Committee.
Senator Ben Cardin, a Democrat from Maryland, emphasized a similar point on Fox.
"These sanctions that have been released are just part of overall sanctions and can be re-imposed at any time," Cardin said. "Congress, I think, will want to make it clear that if Iran does not live up to these commitments, we will not only insist that the sanctions be reapplied, but we will have stronger sanctions against Iran."