NEW YORK – US Secretary of State John Kerry told his former colleagues in the US Senate on Tuesday that he was “not expressing optimism” on the prospect of a deal with Iran over its nuclear program.

Testifying before the Senate Foreign Relations Committee, Kerry said he remained “agnostic” on how the talks in Vienna would conclude.

Those negotiations between Iran and the P5+1 – the US, the United Kingdom, France, Russia, China and Germany – resumed in Austria on Tuesday, with both the US and Iran expressing the belief that talks were “on pace” to begin drafting a final deal next month.

Pressed by committee chairman Sen. Robert Menendez (D-New Jersey) on reports that the US might be willing to settle on Iran’s retention of a limited enrichment capability, Kerry said that achieving “lead time” on Iran’s ability to enrich weapons-grade uranium would constitute significant progress.

“A deal that would ultimately unravel the entire sanctions regime for a six-to-12-month lead time is not far from where we are today,” Menendez said to Kerry.

But Iran requires only two months to break out to that nuclear capability today, Kerry noted in response. The secretary then clarified to the Senate panel what “breakout” technically means: Iran’s decision to produce enough weapons-grade material for a single weapon.

“I think it’s public knowledge today that we’re operating with a time period for a so-called ‘break-out’ of about two months,” Kerry said.

“That’s been in the public domain.”

That does not include weaponization, warhead construction or preparation for delivery, he added.

Nevertheless, he continued, Iran’s decision to break out would be a “huge, consequential decision” that would prompt US President Barack Obama to “respond immediately.”

To lengthen the potential breakout timeline, world powers in Vienna want Iran to cut back the number of centrifuges it operates to refine uranium, and the overall amount of enriched uranium it produces, as well as to limit its research into new technologies and submit to inspections by the United Nations’ nuclear watchdog.

Israel’s position on lengthening that breakout time came up for discussion on Tuesday as well, when Strategic Affairs Minister Yuval Steinitz met with British Foreign Minister William Hague in London.

Steinitz emphasized the importance of preventing Iran from becoming a nuclear threshold state, insisting that its uranium enrichment facilities must be dismantled.

If Iran retains its facilities, Steinitz said, it will remain a nuclear threshold state, because these facilities would allow it to produce a nuclear weapon in a short amount of time.

Such an arrangement, he asserted, “is unacceptable.”

He warned that a nuclear Iran would soon lead to a regional nuclear arms race.

European Union high representative Catherine Ashton and Iranian Foreign Minister Mohammad Javad Zarif chaired the opening session of the Vienna talks Tuesday before handing over the reins to their deputies.

“What matters most to us is that there is a good agreement. Clearly we want to make progress as fast as possible, but the most important thing is the quality of the agreement,” said Ashton’s spokesman, Michael Mann.

“It has to be a good agreement that everyone is happy with. So we will work as hard was we can to achieve that.”

The interim deal forged in Geneva last fall gave the powers six months, until July 20, to negotiate.

“We’re still in an exploratory phase,” one Western diplomat told reporters in Vienna.

“In the end, things will happen in July.”

Tovah Lazaroff and Reuters contributed to this report.


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