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

Bush and Putin were scheduled to hold talks for 90 minutes in the Slovak capital Bratislava, the final stop on a transatlantic visit which Bush hopes will banish lingering bitterness among European allies over the US-led war in Iraq.

Bush began his day by meeting with Slovakia's President Ivan Gasparovic and Prime Minister Mikulas Dzurinda, and was to meet with democratic activists from eastern Europe and make a speech to Slovak citizens in a town square.

But the centerpiece of his day-long stay will be his meeting with Putin, the first US-Russian presidential encounter since their talks on the sidelines of an Asia-Pacific summit in Chile last November, when Bush privately questioned Putin on moves that were widely seen as setting back democracy in Russia.

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 and Putin's disagreements, muted over the past three years by cooperation in the war on terrorism, have grown more vocal since the US president 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 at a joint press conference with European leaders on Tuesday in Brussels.

"But I also will remind him that the United States believes strongly in democratic values," he said.

Bush has stepped up pressure on Iran, which he accuses of trying to acquire nuclear weapons, and on Syria, which he insists must withdraw all of its troops and "secret services" from Lebanon.

Putin has agreed however 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.

The Russian leader has also 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.

But Putin said in an interview with Slovak media: "Democratic institutions should be adapted to today's realities in Russian life, to our traditions and our history."

"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) for international relations," Putin said.

According to a report in The Washington Post, the US and Russian leaders will try to show progress at Thursday's summit by announcing an agreement to counter the threat of nuclear terrorism by speeding up long-delayed security upgrades at Russia's nuclear facilities.

The report came the day after a US intelligence report said theft of radioactive materials at Russia's facilities "has occurred."

The agreement, the details of which the daily said were still being negotiated late on Wednesday, would also develop joint emergency responses to a nuclear or radiological attack and reinforce a program to replace highly enriched uranium in research reactors around the world to prevent it from being used for weapons, the paper said.

"We're trying to demonstrate that we can make progress and move forward despite these other issues," a senior Bush administration official who requested anonymity told The Washington Post.

US officials have said the summit will also yield an agreement to stem the spread of shoulder-fired rockets, which Washington worries could be used by terrorists against civilian airlines.

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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