The leaders, whose once warm relations have cooled since the Iraq war, were to announce two deals -- one to improve security at Russian nuclear sites and the other to curb the spread of shoulder-fired missiles, a Bush aide said.

Ahead of their talks, which were due to last at least 90 minutes, Bush gave his strongest endorsement yet of European efforts to convince Iran not to develop nuclear weapons and said he hoped for a peaceful end to the dispute.

"Hopefully we'll be able to reach a diplomatic solution to this effort. We're more likely to do so when we're all on the same page," said Bush, who in the past has stressed that he cannot rule out using force against Tehran.

Bush's talks with Putin will be their first in person since an Asia-Pacific summit in Chile last November, when the US leader privately questioned his counterpart on moves that were widely seen as setting back democracy in Russia.

Their disagreements, muted over the past three years by the war on terrorism, have grown more vocal since Bush placed a renewed emphasis in his second term on promoting democracy and confronting Iran and Syria.

"It's important for us to keep a constructive relationship with Russia," Bush said in Brussels on Tuesday. "But I also will remind him that the United States believes strongly in democratic values."

"We are against use of this issue as an instrument for fulfilling foreign policy objectives . . . to manipulate in one way or another such a large and important country (as Russia)," Putin said in an interview with Slovak media.

Bush began his day by meeting with Slovakia's President Ivan Gasparovic and Prime Minister Mikulas Dzurinda, before making an emotionally charged speech to thousands of cheering Slovak citizens in a town square.

Bush vowed to stand with Slovakia's young democracy and hailed what he called a "purple revolution" in Iraq, where ink of that color was used to mark those who voted in January 30 elections.

He likened that vote to the Velvet Revolution that broke the hold of communism here nearly 16 years ago, saying: "To the Iraqi people, this is their 1989, and they will always remember who stood with them in their quest for freedom."

With the summit stakes high, Slovakia laid on tight security, deploying more than 5,000 police officers, 400 soldiers as well as emergency workers and firefighters, while two Slovak MIG jet fighters protected the skies with two more MIG's standing by.

Bush was expected to press Putin on Iran, which Washington accuses of trying to acquire nuclear weapons, and on Syria, which Washington insists must withdraw all of its troops ans "secret services" from Lebanon.

Putin has agreed to sell missile systems to Syria, while declaring there is "no evidence" that Iran is seeking an atomic bomb and has stepped up Russian cooperation with Tehran on nuclear technology.

And the Russian leader set off alarm bells in the West with a series of steps seen as autocratic, including moves against the oil giant Yukos, a clampdown on the media, and centralizing political power in the Kremlin.

"Democratic institutions should be adapted to today's realities in Russian life, to our traditions and our history," Putin told Slovak media.

The US and Russian leaders' decision to announce an agreement on securing nuclear materials came a day after a US intelligence report said theft of radioactive materials at Russia's facilities "has occurred."

The details of the plan were unclear, as both sides were still negotiating late Wednesday.

US and Russian officials signed Thursday an agreement to stem the spread of shoulder-fired rockets, which Washington worries could be used by terrorists against civilian airliners.

Meanwhile, about 20 activists from the Greenpeace environmental group demonstrated in Bratislava to urge Bush to fight global warming but the Slovak capital was otherwise calm.

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