WASHINGTON — Iran should be attacked before it develops nuclear weapons, America’s former ambassador to the United Nations said yesterday.

John Bolton, who still has close links to the Bush administration, told the Daily Telegraph that the European Union had to “get more serious” about Iran and recognize that its diplomatic attempts to halt Iran’s enrichment program had failed.

Iran has “clearly mastered the enrichment technology now. … They’re not stopping. They’re making progress, and our time is limited,” he said. Economic sanctions “with pain” had to be the next step, followed by attempting to overthrow the theocratic regime and, ultimately, military action to destroy nuclear sites.

Mr. Bolton’s stark warning appeared to be borne out yesterday by leaks about an inspection by the U.N. International Atomic Energy Agency of Iran’s main nuclear installation at Natanz on Sunday.

The experts found that Iran’s scientists were operating 1,312 centrifuges, the machines used to enrich uranium. If Iran can install 3,000, it will need about one year to produce enough weapons-grade uranium for one nuclear bomb.

Experts had judged that Iran would need perhaps two years to master the technical feat of enriching uranium using centrifuges — and then another two years to produce enough material to build a weapon.

But the IAEA found that Iran has already managed to enrich uranium to the 4% purity needed for power stations. Weapons-grade uranium must reach a threshold of 84% purity.

Mohammed ElBaradei, the IAEA’s head, said the West’s goal of halting the enrichment program had been “overtaken by events.” Iran had probably mastered this process and “the focus now should be to stop them from going to industrial scale production.”

Mr. Bolton said, “It’s been conclusively proven Iran is not going to be talked out of its nuclear program. So to stop them from doing it, we have to massively increase the pressure. If we can’t get enough other countries to come along with us to do that, then we’ve got to go with regime change by bolstering opposition groups and the like, because that’s the circumstance most likely for an Iranian government to decide that it’s safer not to pursue nuclear weapons than to continue to do so. And if all else fails, if the choice is between a nuclear-capable Iran and the use of force, then I think we need to look at the use of force.”

President Bush privately refers to President Ahmadinejad, who has pledged to wipe Israel “off the map,” as a 21st-century Adolf Hitler, and Mr. Bolton, who remains a close ally of Vice President Cheney, said the Iranian leader presented a similar threat.

“If the choice is them continuing [toward a nuclear bomb] or the use of force, I think you’re at a Hitler marching into the Rhineland point. If you don’t stop it then, the future is in his hands, not in your hands, just as the future decisions on their nuclear program would be in Iran’s hands, not ours.”