The White House rejected Iran's contention that its nuclear program is strictly for energy production and expressed deep concern about Tehran's alleged effort to develop atomic weapons.

The administration has long expressed the view that Iran was working on nuclear weapons technology, but new reports suggest the country is moving closer to the goal than international authorities had believed.

"Iran now openly says that it is pursuing the complete nuclear fuel cycle," White House spokesman Ari Fleischer said, referring to the process of exploring for and mining uranium, the raw material needed for nuclear reactors; enriching the uranium; and waste management. Iran denies it trying to build nuclear bombs.

"We completely reject Iran's claim that it is doing so for peaceful purposes," Fleischer said, partly because the country sits on one of the world's largest oil and gas reserves. State Department spokesman Richard Boucher called Iran's nuclear weapons program robust.

Fleischer said Iran tried secretly to build a uranium enrichment plant and heavy water plant, the latter to support a reactor for producing weapons-grade plutonium.

The Washington Post and Time magazine reported that a nuclear power facility at Natanz in Iran is closer to enriching uranium than previously thought. The plant has hundreds of gas centrifuges ready to produce enriched uranium that could be used in advanced nuclear weapons, they reported.

When the project is completed in 2005, Iran will be able to produce enough enriched uranium for several nuclear bombs each year, the Post reported.

An Iranian opposition group reportedly exposed the pilot uranium enrichment plant, an account Fleischer bolstered.

"Iran admitted the existence of these facilities only after it had no choice, only because they have been made public by an Iranian opposition group," he said. "There is no economic justification for this, and it does remain a matter of great concern."

Fleischer said the situation exposed holes in international-inspection efforts -- a point apparently meant to back up President Bush's case in Iraq, where weapons inspectors have reported some cooperation by Baghdad and no evidence of a nuclear program.

The Bush administration appeared to be following a similar course to its North Korea policy, publicly denouncing the nuclear weapons program while trying not to arouse alarm.

Another White House spokesman, Sean McCormack, said the administration is awaiting a report from the International Atomic Energy on its visit to Iran's nuclear facilities last month.

The challenge in discerning Iran's nuclear intentions is heightened by Tehran's "opaque" government, McCormack said.