President Mahmoud Ahmadinejad struck a defiant tone Monday on the 29th anniversary of the Islamic revolution, vowing not to slow Iran's nuclear program and announcing plans to launch more rockets into space as part of its drive to orbit a domestic satellite.

Like Iran's nuclear activities, the country's space program has provoked unease abroad because the same technology needed to send satellites into space can be used to deliver warheads.

Iranian officials insist both the space and nuclear programs are intended for peaceful purposes, and Ahmadinejad rallied Iranians against U.N. Security Council demands that Iran stop enriching uranium.

"I ask the people's view. Would you agree if I ... gave in, surrendered or compromised over the nuclear issue? Would you agree to give up one iota of your nuclear rights?" Ahmadinejad asked hundreds of thousands at a gathering in the capital.

The crowd chanted in response: "No!" and "Nuclear energy is our definite right."

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State TV said millions took to the streets across Iran to mark the anniversary of the 1979 revolution that toppled a pro-U.S. monarchy and brought hard-line clerics to power. Hundreds of thousands marched in Tehran shouting "Death to America" and burning effigies of President Bush and Israeli Prime Minister Ehud Olmert.

Washington has led the push for a third round of sanctions against Iran for ignoring U.N. demands that it suspend uranium enrichment, a technology that can produce nuclear reactor fuel or material for an atomic bomb. Last month, the five permanent Security Council members — the U.S., Russia, China, Britain and France — agreed on a draft resolution for new sanctions.

Ahmadinejad said Monday that Iran won't be frightened by the threat of more sanctions. He also warned the Security Council that it risked losing credibility by relying on U.S.-led questions about Iranian nuclear intentions.

"If (Security Council) powers make any decision against the Iranian nation, they in fact decide against their own credibility," he said.

He was alluding to a U.S. intelligence report in December that concluded Iran stopped a nuclear weapons program in late 2003 and had not resumed it. U.S. officials, however, continue to warn that Iran's enrichment work could easily allow Tehran to resume weapons development.

Ahmadinejad also dedicated Monday's speech to promoting Iran's space program, saying two more research rockets will be fired into space before the first Iranian-made satellite is put into orbit, hopefully by this summer.

Earlier this month, Iran said it launched its first research rocket into space and unveiled its first major space center and an Iranian-built satellite — called the Omid, or Hope.

"Today, we possess all the fundamental sections needed to launch a satellite into space," said Ahmadinejad. "We built all ourselves."

The U.S. called the Feb. 4 rocket launch "just another troubling development" amid concerns about Iran's development of medium- and long-range missiles.

Despite the anxiety over the space program, it is not clear how far along Iran really is, and analysts have expressed doubts about previous Iranian announcements of such technological achievements.

On Monday, Ahmadinejad offered the first details about the Feb. 4 launch. He said the first section of the rocket — the Kavoshgar-1, or Explorer-1 — detached after 90 seconds and returned to earth by parachute. The second segment entered space for about five minutes, he said, and the final section was sent "toward" orbit to collect data.

Iran says it wants to put its own satellites into orbit to monitor natural disasters in the earthquake-prone nation and improve telecommunications. Iranian officials also point to U.S. use of satellites to monitor Afghanistan and Iraq and say they need similar security abilities.

Iran launched its first commercial satellite on a Russian rocket in 2005 in a joint project with Moscow, which appears to be the main partner in transferring space technology to Iran.