VIENNA, May 14 — Inspectors for the International Atomic Energy Agency have concluded that Iran appears to have solved most of its technological problems and is now beginning to enrich uranium on a far larger scale than before, according to the agency’s top officials.

The findings may change the calculus of diplomacy in Europe and in Washington, which aimed to force a suspension of Iran’s enrichment activities in large part to prevent it from learning how to produce weapons-grade material.

In a short-notice inspection of Iran’s operations in the main nuclear facility at Natanz on Sunday, conducted in advance of a report to the United Nations Security Council due early next week, the inspectors found that Iranian engineers were already using roughly 1,300 centrifuges and were producing fuel suitable for nuclear reactors, according to diplomats and nuclear experts here.

Until recently, the Iranians were having difficulty keeping the delicate centrifuges spinning at the tremendous speeds necessary to make nuclear fuel and were often running them empty or not at all.

Now, those roadblocks appear to have been surmounted. “We believe they pretty much have the knowledge about how to enrich,” said Mohammed ElBaradei, the director general of the energy agency, who clashed with the Bush administration four years ago when he declared that there was no evidence that Iraq had resumed its nuclear program. “From now on, it is simply a question of perfecting that knowledge. People will not like to hear it, but that’s a fact.”

It is unclear whether Iran can sustain its recent progress. Major setbacks are common in uranium enrichment, and experts say it is entirely possible that miscalculation, equipment failures or sabotage — something the United States is believed to have attempted in the past — could prevent the Iranian government from reaching its goal of producing fuel on what President Mahmoud Ahmadinejad of Iran boasts is “an industrial scale.”

The material produced so far would have to undergo further enrichment before it could be transformed into bomb-grade material. To accomplish that, Iran would likely first have to evict the I.A.E.A. inspectors, as North Korea did four years ago.

Even then, it is unclear whether the Iranians have the technology to produce a weapon small enough to fit atop their missiles, a significant engineering challenge.

While the United Nations Security Council has passed a resolution demanding that Iran suspend all of its nuclear activities, and it has twice imposed sanctions for Tehran’s refusal to do so, some European nations, and particularly Russia, have questioned whether the demand for suspension still makes sense.

The logic of demanding suspension is that it would delay the day that Iran gained the knowledge to produce its own nuclear fuel — what the Israelis used to refer to as “the point of no return.” Those favoring unconditional engagement with Iran have argued that the current strategy is creating a stalemate that the Iranians are exploiting, allowing them to make technological leaps while the Security Council steps up sanctions.

The Bush administration, in contrast, has argued that it will never negotiate while the Iranians speed ever closer to a nuclear weapons capability, saying there has to be a standstill as long as talks proceed. In a telephone interview, R. Nicholas Burns, the undersecretary of state for policy, who is implementing the Iran strategy, said that while he has not heard about the I.A.E.A.’s newest findings, they would not affect American policy.

“We’re proceeding under the assumption that there is still time for diplomacy to work,” he said, although he added that if the Iranians did not agree to suspend production by the time the leaders of the Group of 8 industrial nations meet next month, “we will move ahead toward a third set of sanctions.”

Mr. ElBaradei has always been skeptical of that strategy, telling European foreign ministers that he doubts the Iranians will fully suspend their nuclear activities and that a face-saving way must be found to resolve the impasse.

“Quite clearly, suspension is a requirement by the Security Council and I would hope the Iranians would listen to the world community,” he said. “But from a proliferation perspective, the fact of the matter is that one of the purposes of suspension — keeping them from getting the knowledge — has been overtaken by events. The focus now should be to stop them from going to industrial scale production, to allow us to do a full-court-press inspection and to be sure they remain inside the treaty.”

The report to the Security Council next Monday is expected to say that since the Iranians stopped complying in February 2006 with an agreement on broad inspections by the agency around the country, the I.A.E.A.’s understanding of “the scope and content” of Iran’s nuclear activities has deteriorated. I

Inspectors are concerned that Iran has declined to answer a series of questions, posed more than a year ago, about information the agency received from a Pakistani nuclear engineer, Abdul Qadeer Khan. Of particular interest is a document that shows how to design the collision of two nuclear spheres — something suitable only for producing a weapon.