Washington, D.C.__ A former senior Obama Administration official told the House Foreign Affairs Committee today that the deal proposed to Iran by the P5+1 countries in Geneva last weekend would “double Iran’s breakout time.”

“That means it would take Iran twice as long” to produce enough highly enriched uranium for a nuclear bomb, former Deputy Assistant Secretary of Defense for the Middle East Colin Kahl told the committee. “That is meaningful. The deal puts firm restrictions on Iran building fuel assemblies for the Arak fuel reactor.” It would “increase the inspections regime. [It] serves US and Israeli interests.”

Kahl testified that under the deal presented by six world powers to Iran at the end of a three day meeting in Geneva last weekend, Iran would suspend 20% enrichment, neutralize its 20% stockpile, refrain from building fuel assemblies at the Arak reactor and from installing new centrifuges, allow more inspections of nuclear facilities, as well as restrict the growth of its 3.5% stockpile.

In return for Iran suspending those activities for 6 months as part of the first phase of a two-part deal, Iran would receive under $10 billion in sanctions relief, including on the auto, gold and petrochemical industries, and access to approximately $3 billion in hard currency assets frozen in banks abroad.

The sanctions relief envisaged in the first phase of the deal involves “nothing permanent if the Iranians reverse course,” Kahl, now associate professor at Georgetown University, said. “Nothing [in it] guts the oil and banking sanctions,” which would be subject to reaching a comprehensive agreement that the parties aim to negotiate during the six month first phase.

“The bigger risk is to escalate the sanctions at a sensitive moment of diplomacy and watch diplomacy careening off the cliff,” Kahl warned.

An Israeli official said Wednesday, however, that the Israeli government assessed that the measures proposed in the phase 1 deal would lengthen Iran’s breakout time by only a few weeks, and would potentially offer Iran many billions of dollars more in sanctions relief.

But an analysis by former weapons inspector David Albright shared with Kahl calculated that removing Iran’s 20% enriched uranium increases the amount of time it would take Iran to produce enough weapons grade uranium for one weapon from 1.3-2.3 months to 3.1-3.5 months, Kahl said.

The House Iran hearing came as the Obama administration mounted a full court press to lobby Congress against moving new Iran sanctions legislation now as negotiations with Iran make headway.

American, European and Iranian negotiators said significant progress was made at three days of talks in Geneva November 9-11th, but it would take at least another meeting to close an agreement. A new meeting between the P5+1 and Iran, at the political director level, is scheduled for next week, November 21-22.

Kerry, Vice President Joe Biden and Under Secretary of State Wendy Sherman met with members of the Senate Banking committee behind closed doors Wednesday to press for a delay in legislation under consideration by the panel to tighten loopholes in existing Iran sanctions.

Advocates of increasing the sanctions now say they would increase western negotiators’ leverage and keep psychological pressure on Iran’s leadership, as well as deter foreign companies looking for a wink to resume business with Iran. But US negotiators insist new sanctions now, when Iran is trying to negotiate a deal, would backfire, and risk Iran retreating from the policy of engagement promoted by the new Hassan Rouhani administration and his foreign minister Mohammad Javad Zarif.

New sanctions now could “wind up setting us back in dialogue that has taken 30 years to be able to achieve,” Kerry said as he arrived at the Senate Banking committee Wednesday. “What we are asking everybody to do, is calm down. Look hard at what can be achieved, what the realities are.”

Western officials say that the six powers achieved consensus on a draft proposal that was presented to Iran’s Zarif only in the last hours of the meeting in Geneva. French foreign minister Laurent Fabius raised objections to the text Kerry had been negotiating with Zarif at a meeting hosted by European Union foreign policy chief Catherine Ashton in Geneva Friday.

Though US President Obama and French President Francois Hollande, in a phone call Wednesday, stressed their joint support for the unified P5+1 proposal,

French ambassador to Israel Patrick Maisonneuve told a press conference in Tel Aviv Wednesday that “all of the world powers that negotiated with Iran in Geneva fell in line with the French position,” Haaretz’s Barak Ravid reported.

American diplomats–excited about the first sustained, direct US-Iran negotiations in thirty years, and concerned about opposition to a deal from Congress, Israel and Sunni Gulf allies–may have underestimated the ambivalence and even resentment some P5+1 partners may have felt about the five hour Kerry-Zarif-Ashton meeting on a draft accord in Geneva Friday in which other P5+1 powers were not included. Some European allies, led by France, may have sought to slow down what they saw as an overly hasty deal, some sources suggested.

“We are negotiating for more than 10 years,” one western diplomat, speaking not for attribution, told Al-Monitor Wednesday. “I think this complex, sensitive question can afford ten more days of negotiations.”

“We made fantastic progress in Geneva,” he added. “We are not far from an agreement.”