Top U.S. officials said Sunday that Iran had advanced its nuclear weapons program beyond what authorities had previously believed, and they used the reports to bolster the American case that Iraq must be disarmed.

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

"We have seen this week Iran has got a more aggressive nuclear program than the [International Atomic Energy Agency] thought it had," Secretary of State Colin Powell said in a televised interview.

"Here we suddenly discover that Iran is much further along, with a far more robust nuclear weapons development program than anyone said it had," Powell said. "It shows you how a determined nation that has the intent to develop a nuclear weapon can keep that development process secret from inspectors and outsiders, if they really are determined to do it, and we know that Saddam Hussein has not lost his intent."

Powell did not answer directly when asked how close Iran is to building a bomb.

Israel destroyed an Iraqi nuclear plant in 1981, and is deeply alarmed by the development in Iran, Time reported.

National security adviser Condoleezza Rice sidestepped a question about whether Israel would be justified in attacking the Iranian plant.

"I'm not going to speculate on what might be the right thing here," Rice said. "What is the right thing is for the international community to get serious about the problems of proliferation, to recognize that there are states that are determined to try and acquire weapons of mass destruction, to deny them the means."