WASHINGTON – President Bush yesterday called on Iran to explain why it had a secretive nuclear weapons program, and warned that any such efforts must not be allowed to flourish “for the sake of world peace.”

“Iran is dangerous,” Bush said after an Oval Office meeting with Italian President Giorgio Napolitano. “We believe Iran had a secret military weapons program, and Iran must explain to the world why they had a program.”

Bush’s comments came after Iranian President Mahmoud Ahmadinejad said that it was “a step forward” that U.S. intelligence agencies had concluded that Tehran stopped developing its nuclear weapons program four years ago.

Ahmadinejad told reporters that an “entirely different” situation between the United States and Iran could be created if more steps like the intelligence report followed.

“We consider this measure by the U.S. government a positive step. It is a step forward,” Ahmadinejad said.

“If one or two other steps are taken, the issues we have in front of us will be entirely different and will lose their complexity, and the way will be open for the resolution of basic issues in the region and in dealings between the two sides,” he said.

Bush did not respond directly to those comments when asked about them in an interview with ABC News yesterday.

“My answer to the Iranians is: You had a hidden program that was a military program,” he said. “We think you have shut it down now. You have an obligation to explain to the world loud and clear why you had a military program. Do you intend to start it up again. In other words, the ball is in their court.”

White House press secretary Dana Perino dismissed Ahmadinejad’s comments as “fanciful thinking.”

Iran has said its nuclear program is peaceful, but until last week, the United States and Western allies had countered that Iran was hiding plans for a bomb.

“Iran has an obligation to explain to the IAEA why they hid this program from them,” Bush said, referring to the nuclear watchdog International Atomic Energy Agency.

“Iran is dangerous, and they’ll be even more dangerous if they learn how to enrich uranium,” Bush said. “So I look forward to working with the president,” Bush said, referring to Napolitano, the Italian leader, “to explain our strategy and to figure out ways we can work together to prevent this from happening for the sake of world peace.”

Bush’s comments amounted to a renewed effort to keep pressure on Iran after the release of last week’s National Intelligence Estimate. That report found that Iran had halted its nuclear weapons program in 2003, and administration officials worry it could weaken their ability to build global pressure on Tehran to stop its uranium enrichment program.

That estimate cautioned that Tehran continues to enrich uranium and still could develop a bomb between 2010 and 2015 if it decided to do so.

It also concluded that it may be difficult to ultimately dissuade Tehran from developing a nuclear bomb because Iran believes such a weapon would give it international prestige and leverage to achieve its national security and foreign policy goals, the assessment concluded.

Iran is still enriching uranium for its civilian nuclear reactors that produce electricity. That leaves open the possibility that fissile material could be diverted to covert nuclear sites to produce highly enriched uranium for a warhead.

Napolitano said he and Bush broadly “share the same concerns, and we express a common commitment” on a variety of issues.

“We want to discuss, constructively, our positions on all questions in all tracks,” he said. “We just want to give our contributions and our ideas on how to face, successfully, all threats, including the very serious threat of nuclear weaponization of Iran.”

Yesterday, diplomats from the U.S., Russia, China, Britain, France and Germany held a 90-minute telephone conference call to discuss a draft plan for new United Nations sanctions against Iran, the State Department said.

“They had a good, constructive conversation and they will continue to work to finalize the elements of a Security Council resolution,” spokesman Sean McCormack said. The diplomats will likely have another discussion soon “with an eye toward in the coming weeks having a final Security Council resolution that can be voted upon,” he added.

He declined to offer specifics of the draft or whether China and Russia, which have resisted new sanctions on Iran, had agreed to it, saying it was too early to say whether there was consensus among the council’s veto-wielding members.

U.S. officials have said the draft discussed yesterday, which was written by the French, includes sanctions against portions of Iran’s military apparatus and a major bank.

Meanwhile, an exiled Iranian opposition group yesterday contested the intelligence report’s finding that Tehran halted a nuclear weapons development program in 2003, insisting the bomb-making program resumed the following year.

“We announce vehemently that the clerical regime is currently continuing its drive to obtain nuclear weapons,” said Mohammad Mohaddessin, a spokesman for the Paris-based National Council of Resistance of Iran.

Associated Press writer Matthew Lee contributed to this report.