TEHRAN — Iran, facing mounting U.S. pressure over its nuclear program, promised yesterday a "scorching hell" for any aggressor as tens of thousands marched to mark the 26th anniversary of its Islamic revolution.

A month after President Bush warned that the United States hasn't ruled out military action against Iran, President Mohammed Khatami responded before a crowd gathered on a snowy square in Tehran.

The U.S. accuses Iran of maintaining a nuclear-weapons program, which Iran says is for peaceful energy purposes.

"Will this nation allow the feet of an aggressor to touch this land?" Khatami asked at the crowd. "If, God forbid, it happens, Iran will turn into a scorching hell for the aggressors."

His statements drew chants of "Death to America!" from the crowd.

Khatami is widely recognized as a leader of a moderate faction in Iran. Indeed, Khatami himself indicated in his speech that the talk of a possible U.S. invasion was pushing him into a united camp with Iran's hard-liners against foreign meddling.

"The Iranian nation is not looking for war, violence and confrontation," Khatami said.

"But the world should know that the Iranian nation won't tolerate any aggression and will stand united against aggression despite differences," he said, referring to the internal divide in Iranian politics between reformers and the more conservative clerics.

Last week, Bush accused Iran of being "the world's primary state sponsor of terror," and last month he said his administration won't rule out using military force against Iran over its nuclear program.

Until Khatami's statements, some had pointed to a possible softening in Iran's position in recent comments made by Iran's top nuclear negotiator, Hasan Rowhani, who said that his country wants to resolve its differences with the United States.

But in his speech yesterday, Khatami was adamant that Iran won't scrap its nuclear program. Iranian scientists worked hard to develop nuclear technology on their own and will not stop due to "the illegitimate demands of others," he said.

"We have decided to move toward scientific progress, including peaceful nuclear technology and we will continue this path," Khatami said.

Khatami said Iran's decision to suspend uranium enrichment in November was a voluntary sign of good will that should be reciprocated by the International Atomic Energy Agency and European negotiators pressing Iran for concessions on its nuclear program.

The suspension, policed by the IAEA, is aimed at building trust and avoiding U.N. Security Council sanctions.

Under an agreement reached with Britain, France and Germany, who negotiated on behalf of the European Union, Iran will continue suspension of its enrichment activities during negotiations with the Europeans about economic, political and technological aid. Iran has said it will decide in three months whether to continue its suspension.

Iranian exiles in Berlin call for democratic changes

BERLIN — Roughly 2,000 Iranian exiles from around Europe marched in Berlin yesterday, calling for democratic change in Iran on the anniversary of the 1979 Islamic Revolution.

A German court lifted a ban imposed earlier in the day by Berlin authorities, freeing the exiles to march toward the Brandenburg Gate in central Berlin, a police spokeswoman said.

Earlier, an interior-ministry spokeswoman had said the demonstration posed a threat to public security and was an action on behalf of the exiled opposition People's Mujahedeen Organization, branded a terrorist group by the United States and European Union.

The rally was transferred to Berlin at short notice after French authorities refused to allow it to take place in Paris. Berlin police said the march had proceeded peacefully.

"We think it is time for the world to take a decisive stance against the regime in Iran," said Ali Safavi of the group's political wing, the National Council of Resistance of Iran.

"The regime in Iran is terrified. The ruling clerics know these are their last days and they tried to stop this democratic demonstration," said Shokrani Taheri, handing out fliers amid police officers at the Brandenburg Gate. "Tehran has made deals with the governments of Europe. There's business and oil and the Europeans don't want to lose them."

Sensing their voices may be eclipsed by international developments, Iranian exiles are lobbying to overthrow the Tehran regime through economic sanctions and support of internal opposition groups.

Many marching in the demonstration complained that European negotiations with Iran have done little to improve Tehran's human-rights record or derail its nuclear program. Protesters said that while they opposed a U.S. military strike on Iran, they were encouraged by tough language directed at the regime by President Bush during his State of the Union address last week and by Secretary of State Condoleezza Rice this week.

Rice has said an attack on Iran is "simply not on the agenda" at this time.