A bipartisan group of senators is readying legislation for additional sanctions on Iran -- hoping for a vote by year’s end or in early January -- despite pleas Tuesday from Secretary of State John Kerry to hold off and threats from Iran’s foreign minister that congressional action would scuttle a delicate nuclear deal forged last month.

The United States, China, Russia, France, the United Kingdom, plus Germany (the so-called P5+1) signed an interim agreement Nov. 24 that calls on Iran to freeze nuclear weapons development and comply with stringent verification and inspections, in exchange for a partial loosening of economic sanctions estimated to be worth $7 billion. The interim deal is intended to lead to a permanent, verifiable agreement.

The lobbying effort by Kerry and President Obama may have persuaded some lawmakers, and combined with a packed year-end calendar and some slow walking from Democratic leadership, the administration could stave off a vote in the final weeks of the year.

“There’s not going to be a vote on Iran sanctions this month. I don’t think Harry [Reid] is going to allow that to happen,” Republican Sen. Bob Corker, the ranking member of the Foreign Relations Committee, told RCP. “I think if he allows something to be voted on, it would be something that is meaningless.”

Reid, the Senate majority leader, said Monday there would be a debate in the next two legislative weeks on Iran sanctions, but he has not promised a vote. Reid is caught between a White House that wants Congress to let the deal with Iran stand and lawmakers -- including many in his own party -- calling for legislative action to toughen the agreement.

One of them, Senate Banking Chairman Tim Johnson, agreed Tuesday to hold off on sanctions legislation in his committee, saying he was convinced by Kerry’s testimony before the House Foreign Affairs Committee earlier that day. Democratic Sen. Chuck Schumer, a strong supporter of Israel -- which opposes the sanctions agreement -- was mum on Tuesday, telling reporters he would not comment on the issue.

The bipartisan drive on Capitol Hill to consider tougher sanctions reflects Americans’ deep distrust of the Islamic nation as well as sympathy with Israel that negotiators cut a bad deal with Tehran.

But leaders in both nations find themselves at a critical juncture, given that they are in talks for the first time in more than three decades, even as hard-liners in each country openly express skepticism. President Hassan Rouhani, a political moderate elected by Iranians to end the debilitating international sanctions, must appease the ruling Islamic supreme ayatollah. Obama, who has labored under gyrating job approval ratings and harsher assessments of his credibility and competence, wants to reassure Americans, nervous members of his party, and Israelis who worry they’re targeted by a nation that has publicly denied their right to statehood.

Foreign Minister Mohammed Javad Zarif warned last week that if Congress adopts new sanctions -- even if triggered after the temporary deal’s May deadline -- all bets are off.

“The entire deal is dead,” he told Time magazine Dec. 7. “We do not like to negotiate under duress. And if Congress adopts sanctions, it shows lack of seriousness and lack of a desire to achieve a resolution on the part of the United States. I know the domestic complications and various issues inside the United States, but for me that is no justification.”

Some vehicles for sanction legislation have already been blocked, including a proposed Defense Authorization renewal that involves no additional amendments. (Some senators, however, signaled they would vote against the bill in that form.) Minority Leader Mitch McConnell said Reid employed the tactic to avoid a vote on sanctions.

Still, Democratic Sen. Robert Menendez, chairman of the Foreign Relations Committee, is pushing forward with legislation, undeterred by Kerry or the administration.

Menendez is leading on a bill with Republican Sen. Mark Kirk that would potentially impose sanctions targeting oil exports; additional sectors of the Iranian economy, including construction and energy projects; foreign exchange reserves; and assets of key regime officials, a Senate aide familiar with the talks told RCP. The measure “acts as an insurance policy if Iran breaks the current deal,” the aide said, noting the legislation would allow the president flexibility in negotiating a final, long-term deal while holding Iran’s feet to the fire.

The measure is similar to one passed by the House this summer with wide bipartisan support, 400-20. Some House Republicans are urging the Senate to take up that bill. Others, like Eric Cantor, are working on legislation to define the goals of a final deal, an approach that could gain Democratic support.

Menendez disagreed with the administration’s contention that new sanctions will undermine the P5+1 pact. The New Jersey senator told reporters that legislation would be released before he and his colleagues recess at the end of next week.

Kerry urged lawmakers to wait while the United States and other nations craft the longer-term deal, assuring them that the administration will ask Congress to approve sanctions eventually -- if they are needed:

“I'm asking you not to do it now, because of the . . . relationship with our P5+1 and the message that it sends. But you're wrong when you say that the administration is not going to come and ask for [sanctions]. You're just dead wrong. We're telling you, we will."

Still, House members from both sides of the aisle were skeptical about the current deal, and remain concerned that Iran won’t agree to anything beyond it. “I don’t think it’s asking too much from Iran to say, ‘At least while we’re talking, you stop enriching,’ ” Democratic Rep. Eliot Engel, the ranking member of the Foreign Affairs Committee, told Kerry.

“The key issue is whether a final agreement would allow Iran to manufacture nuclear fuel,” Chairman Ed Royce said. “It simply can’t be trusted with enrichment technology, because verification efforts can never be foolproof.”

For the first time since the imposition of United Nations and other world sanctions, the current agreement would permit Iran to enrich uranium to 5 percent for “peaceful” use, chiefly power. Obama denied last week that Tehran would be granted a “right to enrich” beyond that.

“I want to be very clear there’s nothing in this agreement or document that grants Iran a right to enrich,” he said Saturday during a question-and-answer event at the Saban Forum, a gathering organized by the Brookings Institution. “We’ve been very clear that given its past behavior, and given existing U.N. resolutions and previous violations by Iran of its international obligations, that we don’t recognize such a right.”

Nonetheless, South Carolina Sen. Lindsey Graham said new sanctions proposed by Congress are intended to “get a good outcome. What is a good outcome? A good outcome is a peaceful nuclear power program in Iran where internal community controls the fuel cycle.”

Graham said sanctions would kick in at the end of six months if Iran did not dismantle its plutonium reactor. And, he said, “if they're still in the enrichment business, the sanctions stay in place.”

Though the testing period with Iran is six months, Kerry told impatient House members on Tuesday that Tehran could speed things up. "It's up to Iran, really, to decide how fast they want to prove this," the secretary said during his House testimony, which he will repeat later this week in the Senate.