Secretary of State John Kerry has told US lawmakers any new sanctions against Iran would risk ruining talks over Tehran's nuclear programme, BBC reported.
He told a Senate banking committee that the US might lose negotiating partners if it imposed economic penalties.
The panel has been considering a fresh package but legislators are divided on the measure.
Mr Kerry has told the BBC that Iran and world powers had come "extremely close" to a deal at the weekend.
Before Wednesday's closed-door meeting with senators, Washington's top diplomat told reporters: "What we're asking everybody to do is calm down, look hard at what can be achieved and what the realities are."
None of the differences between the so-called P5+1 - the US, UK, France, Russia and China plus Germany - and Iran over its nuclear programme are big enough to prevent agreement, Mr Kerry has previously said.
Moving too quickly?
With the negotiators due to meet again on 20 November, both Republicans and Democrats have argued that a new round of sanctions targeting the oil and banking industries of Iran could serve as a bargaining chip in the talks.
The P5+1 has considered offering relief to Tehran on some sanctions in exchange for nuclear concessions.
Negotiations are expected to resume later this month in Geneva.
The Obama administration has offered Iran some of its frozen overseas assets if the country agrees to a deal.
But it has insisted that the strictest restrictions should remain in place until Iran conclusively proves it is not trying to assemble nuclear weapons. Iran says it is just a civilian energy programme.
Some US legislators believe the White House is moving too quickly.
In a separate hearing, several House legislators said the US should take a harder line with Iran.
"The Iranian regime hasn't paused its nuclear programme," said Representative Ed Royce, a Republican.
"Why should we pause our sanctions efforts as the administration is pressuring Congress to do?"
The BBC's Capitol Hill producer Suzanne Kianpour says that, according to senior administration officials, Mr Kerry - as well as Vice-President Joe Biden - will continue to shuttle back and forth to Congress to lobby lawmakers against proposing new sanctions.
ANN.Az
