Secretary of State John Kerry pressed senators on that point last week, saying a tighter sanctions regime would be counter-productive.

“It could destroy the ability to get agreement, and it could actually wind up setting us back in dialogue that has taken 30 years to be able to achieve,” said Kerry.

So-called P5+1 negotiations with Iran are to resume this week in Geneva. Tehran is demanding an end to international sanctions while asserting a right to continue enriching nuclear material.

Israeli Prime Minister Benjamin Netanyahu has blasted any deal that eases sanctions before Tehran verifiably eliminates its nuclear military capability. Secretary Kerry will attempt to assuage Israeli concerns when he meets with Netanyahu later this week.