Iran has accelerated its deployment of advanced uranium enrichment centrifuges in the past two years, a new report by the authoritative Washington-based Institute for Science and International Security warned on Thursday.

The report, co-written by the institute’s founder, former U.N. weapons inspector David Albright, noted that the acceleration occurred in the past two years, following a three-year lull created by the 2015 nuclear deal.

“Iran has demonstrated its commitment to replace the IR-1 centrifuge with advanced centrifuges, which can produce considerably more enriched uranium,” said the report.

“Iran’s plans and declarations to the IAEA [International Atomic Energy Agency] show that it intends to install many more advanced centrifuges in the coming months, further increasing its enrichment capacity,” it stated. “Unless compensatory steps are taken, such as destroying rather than mothballing advanced centrifuges, a renewed JCPOA [Joint Comprehensive Plan of Action] will not maintain a 12-month breakout timeline to produce enough weapons-grade uranium for a nuclear weapon. If Iran mothballs its advanced centrifuges, timelines of only five to six months are likely.”

Nuclear talks between Iran and world powers are underway in Vienna.

In November, the institute noted in a report that Iran has enough enriched uranium in the form of near 20 percent and 60 percent enriched uranium to produce enough weapons-grade uranium—25 kilograms—for a single nuclear weapon “in as little as three weeks.”

The report warned that “the growth of Iran’s stocks of near 20 and 60 percent enriched uranium has dangerously reduced breakout timelines.”