That report will come less than three weeks before planned talks between Iran and the world's five powers _ the US, Russia, China, Britain, France and Germany _ designed to reduce concerns about Tehran's nuclear agenda.

Iran's enrichment program has come under renewed focus with the conclusion of cyber experts and analysts that the Stuxnet worm that 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.

The worm "specifically controls frequency converter drives" that normally run between 807 Herz and 1210 Herz, researcher Eric Chien of the computer security company Symantec, said in an e-mail. "These are subsequently changed to run at 1410Hz, then 2Hz, and then 1064Hz."

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 signs of covert proliferation.

Albright and a colleague, Andrea Stricker, last week released a study applying Chien's finding to centrifuges. He 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, another official from an IAEA member country suggested the worm could cause further damage to Iran's nuclear program.

The official also 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.

There was no independent confirmation. But nuclear experts have suggested that the worm's pervasive invasion of Iran's nuclear program could result in a series of problems.

Commenting on Stuxnet Monday, Olli Heinonen, the IAEA's former point man on Iran, told a Washington audience that the virus could have infected control systems at Bushehr "or elsewhere."

"It may cause a lot of havoc," he said.