Iran can enrich enough weapons-grade uranium for a single nuclear bomb in about a month, according to an estimate by a nuclear non-proliferation think tank released late Wednesday.

The report, by the Washington-based Institute for Science and International Security, claims Iran has significantly shortened the time needed to “break out” to a nuclear bomb with the installation of new centrifuges in the Fordo and Natanz plants, and advanced IR-2 machines at Natanz.

According to ISIS, which has tracked Iran’s nuclear program for several years, Tehran could have enough uranium for a nuclear bomb in 1–1.6 months by converting all of its 20-percent enriched stockpile. Using only 3.5% enriched uranium, Iran could have four nuclear bombs in about two months, the group estimates.

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Using new IR-2 centrifuges, which are currently being installed in Natanz, the time could be shortened to just a week or two, according to the study.

“The shortening breakout times have implications for any negotiation with Iran. An essential finding is that they are currently too short and shortening further, based on the current trend of centrifuge deployments,” the report reads.

The news comes amid intensifying talks between Iran and six world powers over curbing Tehran’s nuclear program in return for sanctions relief. A new round of talks is planned for early November, when the US, UK, France, China, Russia and Germany will reportedly discuss accepting a proposal to let Iran continue enrichment to 20 percent, with safeguards in place.

Israel has called for the international community to continue sanctioning the regime in Tehran until it gives up all enrichment, saying even a small amount would allow Iran to break out to the bomb.

Iran claims its nuclear program is peaceful.

Senator Mark Kirk, who sits on a Banking Committee considering hiking sanctions on Iran, told USA Today the US needs to tighten penalties on Iran in light of the report.

“The Senate should move forward immediately with a new round of sanctions to prevent Iran from acquiring an undetectable breakout capability,” he said.

The ISIS report cautions that times for weaponizing the uranium could vary significantly depending on how far along Iran is in building a delivery system for a bomb.

“If Iran successfully produced enough [weapons-grade uranium] for a nuclear weapon, the ensuing weaponization process might not be detectable until Iran tested its nuclear device underground or otherwise revealed its acquisition of nuclear weapons,” it reads.

The report calls for negotiators to push for increased transparency; halting enrichment to 20% and shipping out or degrading existing stocks; and a series of measures meant to lengthen the potential breakout to six months or longer, enough time for the International Atomic Energy Association to detect the move.

On Wednesday, an Iranian lawmaker said Iran had no more need for 20% enriched uranium and had stopped upgrading to that level. Hossein Naqvi Hosseini, who serves as a spokesman for the Iranian parliament’s national security and foreign policy committee, also said the country is prepared to relieve concerns over its stockpile of enriched uranium.

“Tehran is ready to convert its stockpile of 20% enriched uranium to fuel rods and remove concerns over its non-peaceful use,” he was quoted as saying. He offered no other details about what steps Iran would take.

Iran is also in the midst of negotiations with the IAEA over expanding access to nuclear watchdogs. Though talks over the matter have failed to advance in two years, the UN agency on Wednesday confirmed that Tehran would send Deputy Foreign Minister Abbas Araghchi, its top nuclear negotiator, to an upcoming meeting.

In October 2012 ISIS — which often advises Congress and other branches of US government on Iran’s nuclear program — estimated that Iran could make enough uranium for a bomb in two to four months.

The Associated Press contributed to this report.

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