WASHINGTON – Legislation to impose tough new sanctions on Iran could come to the US Senate floor this week, just as diplomats head to Geneva for a third round of talks aimed at curbing Tehran’s suspected nuclear weapons work.

President Barack Obama has appealed to Congress to hold off on new sanctions to allow time to pursue a diplomatic deal. But Congress is generally more hawkish about Iran than the administration, and both Republicans and some of Obama’s fellow Democrats have balked at any further delay.

Several Republicans, frustrated that the Senate Banking Committee had delayed a tough new sanctions package at the White House’s request, said that they were considering forcing the issue by offering more restrictions on Iran as an amendment to a defense authorization bill expected to come to the Senate floor by the middle of next week.

“That means we get the defense bill on the eve of ‘Geneva, Part Three,’ and all of this back-and-forth between Congress and the White House comes to a head,” a senior Senate aide said.

The issue of sanctions on Iran is a rare area where US Republicans and Democrats work together. Supported by the influential pro-Israel lobby, measures condemning Iran pass both houses of Congress by overwhelming margins.

The House of Representatives approved its tighter sanctions bill in July by a vote of 400 to 20.

As the debate went on, lawmakers both for and against an increase in sanctions issued statements spelling out their positions.

Four Republican senators – Mark Kirk of Illinois, Marco Rubio of Florida, John Cornyn of Texas and Kelly Ayotte of New Hampshire – wrote to Obama expressing deep concern about the negotiations. The letter, obtained by Reuters on Friday, cited reports that Iran would obtain up to $20 billion in sanctions relief but not be required to shut down centrifuges, close facilities or get rid of enriched uranium.

The senators explained their concerns, and said that tough new sanctions should be put in place to increase pressure on Iran.

“Rather than forfeiting our diplomatic leverage, we should increase it by intensifying sanctions until Iran suspends its nuclear and ballistic missile programs in accordance with multiple Security Council resolutions,” the four senators wrote.

But California Senator Dianne Feinstein, a senior Democrat who is chairwoman of the Senate Intelligence Committee, said that she “strongly opposed” any attempt to increase sanctions on Iran while the “P5+1” talks between Tehran, western powers, China and Russia continued.

“Tacking new sanctions onto the defense authorization bill or any other legislation would not lead to a better deal. It would lead to no deal at all,” Feinstein said in a statement. “I am baffled by the insistence of some senators to undermine the P5+1 talks. I will continue to support these negotiations and oppose any new sanctions as long as we are making progress toward a genuine solution.”

Senator Ted Cruz (R-Texas) told a group of congressmen on Thursday afternoon that he supports new sanctions legislation, and accused the Obama administration of giving away its leverage with Iran through a bad deal. This is the time for more sanctions, he said, adding that Obama was degrading the US-Israel relationship by grasping for “any deal” it could achieve.

“I think it is likely the Senate will debate it in the next couple of weeks,” Cruz told The Jerusalem Post after his speech. “The exact timing is up in the air, but I’m hopeful it’ll be sooner rather than later.”

On whether he thought the bill would proceed independently or as an amendment to the defense authorization bill, Cruz said: “That’s a question still up for debate.”

The senator was one of many prominent figures to address the Israel Allies Foundation on Thursday during its 2013 conference.

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