Secretary of State John Kerry on Thursday asked U.S. senators pressing for tougher sanctions over Iran's nuclear ambitions to be patient, saying there is uncertainty in the Islamic republic two months before its June 14 election.
"I think this is a moment for us to be a little patient," Kerry said at a hearing of the Senate Foreign Relations Committee.
"I do think timing and the choice of when we might do something is critical. We need to cooperate together on that," he said, adding that President Barack Obama's administration is monitoring the situation closely, and working with allies.
Western powers suspect Iran is trying to develop the means to produce nuclear weapons under the guise of a declared civilian atomic energy program. Iran denies the accusation.
Some U.S. lawmakers have been pushing hard for Washington to do more - including imposing even tighter sanctions - to clamp down on Iran.
The Senate Foreign Relations Committee on Tuesday passed a resolution saying Iran's pursuit of nuclear weapons poses an international threat, urging full implementation of sanctions and calling on the Obama administration to strengthen their enforcement.
Israel, Iran's arch-enemy, has grown impatient with protracted talks and has threatened pre-emptive war against Tehran if it deems diplomacy ultimately futile.
Kerry stressed that Obama is determined Iran will not succeed in acquiring a nuclear weapon and noted that his administration is working closely with Israel. "We are deeply engaged with our Israeli allies, friends, comparing on a regular basis. I think we're on the same page," he said.