President Bush says Iran must explain why it hid a past nuclear weapons program from United Nations inspectors. VOA White House Correspondent Scott Stearns reports, Iran says it is enriching uranium only for a peaceful civilian program to generate electricity.

President Bush is trying to keep international pressure on Iran after last week's National Intelligence Estimate found that Tehran stopped its nuclear weapons program four years ago.

Mr. Bush says the U.S. intelligence report proves that Iran was lying to the U.N.'s International Atomic Energy Agency.

"Iran must explain to the world why they had a program. Iran has an obligation to explain to the IAEA why they hid this program from them," he said. "Iran is dangerous, and they will be even more dangerous if they learn how to enrich uranium."

The president spoke following a meeting with Italian President Giorgio Napolitano during which the two men discussed the nuclear standoff.

Iran's Fars news agency says Tehran has begun a new round of talks with U.N. experts who are seeking information on past nuclear activities.

Iranian President Mahmoud Ahmadinejad says the latest U.S. intelligence report is a step forward. He told reporters if further such steps are taken, the way will be open for resolving regional and bilateral issues

White House Spokeswoman Dana Perino called this "fanciful thinking."

"It's a very opaque society in Iran," she said. "The president asked for more information from our intelligence community. He got more information. And it confirmed what he thought to be true, which is that Iran was a threat, is a threat, and will certainly continue to be a threat if we don't stop them from obtaining that capability to have a nuclear weapon."

The Bush administration is pushing for another round of U.N. sanctions against Iran. Officials from the United States, Britain, France, Russia, China, and Germany are to discuss the draft of a new sanctions resolution Tuesday.

President Ahmadinejad says there is no legal basis for new sanctions against Iran.