TEHRAN, Iran, (AP) – Iran’s nuclear chief said Tuesday that a malicious computer worm known as Stuxnet has not harmed the country’s atomic program and accused the West of trying to sabotage it.

Vice President Ali Akbar Salehi’s remarks came a day after diplomats told The Associated Press in Vienna that Iran’s nuclear program has suffered a recent setback, with major technical problems forcing the temporary shutdown of thousands of centrifuges enriching uranium.

Salehi said details about the virus became known only after Iran’s “enemies failed to achieve their goals.”

Iran has earlier confirmed that Stuxnet infected several personal laptops belonging to employees at the Bushehr nuclear power plant but that plant systems were not affected.

The West has accused Iran of using the nuclear program to develop an atomic weapon. Tehran dismisses the charge, saying the program is for peaceful purposes only and insists it has every right under the Nuclear Nonproliferation Treaty to enrich uranium and produce nuclear fuel.

According to reports released by the U.N. nuclear watchdog, the International Atomic Energy Agency, the Iranian uranium enrichment capacity has stagnated in recent years after initial rapid growth. Tehran has taken hundreds of centrifuges off line over the past 18 months, prompting speculation of technical problems.

At the Natanz enrichment facility in central Iran, the number of operating centrifuges declined from 4,920 in May 2009 to 3,772 in September 2010, the IAEA said.

Suspicions have focused on the Stuxnet worm, the computer virus thought to be aimed at Iran’s nuclear program, which experts last week identified as being calibrated to destroy centrifuges by sending them spinning out of control.

Salehi said Stuxnet sought to find its way into Iran’s nuclear program in 2009 but Iranian experts prevented this.

“From more than a year ago, Westerners tried to implant the virus into our nuclear facilities in order to disrupt our activities but our young scientists stopped the virus at the very same spot they wanted to penetrate,” Salehi said in comments carried by state TV website.

“The Westerners are speaking up a year after they learned that they failed,” Salehi said.

The IAEA is expected to release Tuesday a confidential update on Iran — the latest report by the Vienna-based agency to its 35-nation board on its attempts to get an overview of Tehran’s nuclear activities.

That report will come less than three weeks before planned talks between Iran and the world’s six powers — the U.S., Russia, China, Britain, France and Germany — designed to reduce concerns about Tehran’s nuclear agenda. The report is expected to again focus on Tehran’s refusal to heed U.N. Security Council demands to stop enrichment.

Iran’s enrichment program came under renewed focus with the conclusion of cyber experts and analysts that the Stuxnet worm that they claimed infected Iran’s nuclear program was designed to abruptly change the rotational speeds of motors such as ones used in centrifuges. Such sudden changes can crash centrifuges and damage them beyond repair.

No one has claimed to be behind Stuxnet, but some analysts have speculated that it originated in Israel.

Iran nuclear expert David Albright said it was impossible to say what would cause a disruption strong enough to idle the centrifuges but “Stuxnet would do just that.”

“It would send (centrifuge) speeds up and then suddenly drop them,” said Albright of the Washington-based Institute for Science and International Security, which has tracked Iran for possible signs of covert proliferation.

Albright said the worm appeared capable of pushing centrifuge speeds above their normal speeds, up to 1,410 Herz, or cycles per second, and then suddenly dropping speeds to 2 cycles per second, disrupting their operations and destroying some in the process.

Separately, an IAEA member country official suggested the worm could cause further damage to Iran’s nuclear program. The official asked for anonymity because his information was privileged.

He cited a Western intelligence report suggesting that Stuxnet had infected the control system of Iran’s Bushehr reactor and would be activated once the Russian-built reactor goes on line in a few months.

Stuxnet would interfere with control of “basic parameters” such as temperature and pressure control and neutron flow, that could result in the meltdown of the reactor, raising the specter of a possible explosion, he said.