SALZBURG, Austria (AP) — Iran is poised to double its output of higher-enriched uranium at its fortified underground facility, the U.N. nuclear agency said Friday — a development that puts Tehran within months of being able to make the core of a nuclear warhead.

In its report, the International Atomic Energy Agency said Iran was ready within days to ramp up its production of 20 percent enriched uranium at its plant at Fordo using 700 more centrifuges.

That would double Iran’s present output and cut in half the time it would take to acquire enough of the substance needed to make a nuclear weapon, reducing it to just over three months.

Iran says it has no interest in making nuclear arms, just nuclear power for its citizens, but the United States and other nations believe otherwise. Iran refuses to give up enrichment despite international sanctions and offers of reactor fuel from abroad and for years has stalemated an IAEA probe of suspicions that it worked secretly on developing such arms.

The IAEA report, which was circulated among the IAEA’s 35 board member states, was obtained by The Associated Press. It said between the last IAEA board report in August and now, Iran had put nearly 700 centrifuges that were installed but not ready to operate at Fordo under a vacuum to make sure they are airtight.

That is the last step before uranium gas is fed into the centrifuges and the process or enrichment begins — an activity that can produce both reactor fuel, or at high levels the fissile interior of a nuclear weapon. It takes only a few days to start enrichment with machines that are under vacuum.

The centrifuges, “having been subjected to vacuum testing, were ready for feeding” with uranium gas, the report said.

About 700 centrifuges have been producing 20 percent uranium at Fordo since early this year — the same number as those the IAEA said were under vacuum and ready to enrich. Another 1,400 or so have been installed but are not yet believed operational — about 2,800 total.

The finding confirmed information the AP obtained Thursday from diplomats accredited to the IAEA. It also called into question recent comments by Israeli officials suggesting that Iran has slowed the timetable for reaching the ability to make such weapons.

The discrepancy is important because the comments carried the implication that Israel would therefore have more time before deciding whether to hit Iranian facilities in an attempt to slow Tehran’s perceived efforts to make nuclear weapons.