(JTA) — Iran could produce enough weapons-grade uranium to build a nuclear bomb in as little as a month, according to a new estimate by a top American think tank.

“Today, Iran could break out most quickly using a three-step process with its installed centrifuges and its low-enriched uranium stockpiles as of August 2013. In this case, Iran could produce one significant quantity in as little as approximately 1.0–1.6 months, if it uses all its near 20 percent low-enriched uranium hexafluoride stockpile,” the Institute for Science and International Security wrote in a report published on its website Thursday.

The new assessment comes as the White House invited Senate staffers to a briefing on negotiations with Iran as part of its efforts to persuade Congress not to go ahead with a bill to stiffen sanctions against Iran.

“Shortening breakout times have implications for any negotiation with Iran,” stated the report. “An essential finding is that they are currently too short and shortening further.”

David Albright, president of the institute and a former inspector for the U.N. International Atomic Energy Agency, was quoted by USA Today as saying the estimate means that Iran would have to eliminate more than half of its 19,000 centrifuges to extend the time it would take to build a bomb to six months.

The Obama administration has said Iran is probably a year away from having enough enriched uranium to make a bomb.
The White House has said new sanctions legislation should wait while current negotiations — which began last week and are scheduled to resume officially in Geneva next month — are underway.

But Israeli Intelligence and International Affairs Minister Yuval Steinitz has said that Iran had made no concrete offer to resolve the conflict around its nuclear program during the last round of talks.

He made the statement during talks Wednesday with U.S. officials in Washington over Israeli-American strategic cooperation, Israel’s Army Radio reported Friday. “Teheran made no offer to resolve the crisis,” Steinitz was quoted as saying.

Reports by the Associated Press and other media, however, said Iran submitted a proposal to the six world powers involved in the talks: the United States, Russia, China, Britain, France and Germany.

No details of the proposal were made public but Western officials meeting with Iranian negotiators indicated interest, AP reported.

“The talks in Geneva were just feelers,” Steinitz was further quoted as saying.