LONDON -- Iran has told the United Nations nuclear supervisory body that it plans to install more sophisticated equipment at its principal nuclear enrichment plant, a diplomat said on Thursday, enabling it to greatly accelerate processing of uranium in a move likely to worry the United States, Israel and the West.
The diplomat, based in Vienna, the headquarters of the International Atomic Energy Agency, cited a letter from Iranian officials to the I.A.E.A. saying it wants to upgrade its main enrichment plant at Natanz. The upgrade could speed up enrichment by as much as two or three times, the diplomat said, requesting anonymity in light of the confidential nature of the Iranian note.
The United States and its allies accuse Tehran of seeking the technology for nuclear weapons, but Iran says it wants to use enriched uranium purely for civilian and peaceful purposes.
The disclosure came at a time of high regional tension, a day after American officials said Israeli warplanes struck deep inside Syrian territory. The American officials said they believed the target was a convoy carrying sophisticated antiaircraft weaponry on the outskirts of the Syrian capital, Damascus, that had been intended for the Hezbollah Shiite militia in Lebanon.
Iran is a close regional ally of Syria and Hezbollah. While an accelerated Iranian nuclear program would add to regional uncertainties -- possibly renewing Israeli threats to strike at Iran's nuclear facilities -- there was no immediate indication that the timing of Iran's note to the I.A.E.A. was related to the events in Syria.
International negotiations on the nuclear program are stalemated by disagreement over the venue and date for the next encounter between Iranian negotiators and outside powers.
Iranian officials offered no immediate comment on the note, but nuclear experts said Iran's ambitions to install more sophisticated centrifuges had been known for some time. President Mahmoud Ahmadinejad of Iran first hinted publicly that Iranian scientists were conducting research to make these machines back in 2006. According to news reports, Tehran began testing prototypes in 2010.
It was unclear from the Iranian note whether the new centrifuges would be used to enrich uranium to the roughly 4 percent purity level used for civilian power generation, or to the 20 percent purity level that can be used in medical isotope production. The higher purity is more worrisome to Iran's adversaries because it is a short technical step away from the highly enriched uranium used in nuclear weapons.
Cliff Kupchan, an Iran specialist at the Eurasia Group, a Washington-based risk consultancy, said in a note to clients on Thursday that the faster centrifuges, assuming they work well, "would mark a significant technological breakthrough" that theoretically could shorten the amount of time Iran would need to create fuel for nuclear weapons should it choose that path.
But Mr. Kupchan cautioned that "Iran has a long history of overstating its capabilities, and both the number of machines that Iran can deploy and their effectiveness is not yet known." News of the Iranian note emerged days after Iran said it lofted a monkey into space as a prelude to human spaceflight in several years' time.
While American analysts said the missile technology used in the experiment appeared to have little military relevance, James E. Oberg, a former NASA engineer and author of a dozen books on human spaceflight, said Iran's civil space advances also had propaganda value because the peaceful flights could take global attention off the nation's military feats and ambitions.
"Like the North Koreans, they get to present their program as peaceful when lots of it has to do with weapons development," Mr. Oberg said.
The diplomat, based in Vienna, said the I.A.E.A. director general, Yukiya Amano, had circulated a note to the organization on Wednesday saying Iranian officials had informed the watchdog on Jan. 24 that "centrifuge machines type IR2m will be used" in a part of the Natanz enrichment plant.
The I.A.E.A. replied on Jan. 29, seeking technical information about the plan, Mr. Amano's note said.
Currently, Iran uses less reliable IR1 models developed in the 1970s, but has been reported for several years to be trying to enhance its enrichment capability with newer centrifuges developed domestically from technology initially acquired from Pakistan.
Last week, Israel's departing defense minister, Ehud Barak, said that the Pentagon had prepared sophisticated blueprints for a surgical operation to set back Iran's nuclear program should the United States decide to attack -- a statement that was a possible indication that Israel might have shelved any plans for a unilateral strike, at least for now.
Iran's nuclear program also faces a threat of sabotage since a computer worm known as Stuxnet was used to attack its centrifuges more than two years ago. American intelligence officials believe the attack caused many of the machines to spin out of control and self-destruct, slowing the Iranian program's progress.
The Natanz plant, southeast of Tehran, has been used to enrich uranium at low levels. But a newer uranium enrichment plant, known as Fordo, near the holy city of Qum, has raised Western concerns because it is buried deep underground, making it more impervious to scrutiny or attack.
The Fordo plant takes uranium fuel that has been enriched to 4 percent purity at Natanz and further enriches it to 20 percent purity.
Rick Gladstone contributed reporting from New York.
This article originally appeared in The New York Times.