U.S. President George W. Bush and Russia's Vladimir Putin will try to ease strains over missile defence and NATO expansion and polish their legacies at a farewell summit on the Black Sea starting on Saturday.

Fresh from a NATO conference in Bucharest that yielded mixed results for his pet projects, Bush will wrap up a brief trip to Croatia and fly to Russia for his last one-on-one talks with Putin before the Russian president's term ends in May.

Bush hopes to capitalise on a less strident tone struck by Putin at the NATO summit, where he complained of what he called emerging threats to Russia's security but implored alliance leaders: "Let's be friends, guys."

Seven years after saying he had peered into Putin's soul and trusted him, Bush - also in the twilight of his presidency - has hailed the meeting at a seaside compound in Sochi as their last chance for a "heart-to-heart."

No one expects any big breakthroughs but aides say the two leaders are likely to agree on a "strategic framework" for U.S.-Russia relations to bequeath to their successors.

Bush is out to salvage a foreign policy legacy dominated by the Iraq war, which has damaged U.S. credibility.

He is also struggling to stay relevant on the world stage now that his economic stewardship is under fire and attention is focused on whomever will succeed him in January 2009.

For his part, Putin is looking for a smooth transition of Russia's presidency to his protege, Dmitry Medvedev.

Bush will hold separate talks with Medvedez on Sunday and possibly have a chance to gauge how much power Putin, who will become prime minister, will continue to wield at the Kremlin.

SHARP DIFFERENCES REMAIN

Putin reaffirmed to NATO leaders in Bucharest that he remains fiercely opposed to NATO's ambitions for further eastward expansion on Russia's borders and to a planned U.S. missile defence shield based in parts of Eastern Europe.

But he stopped short of the searing attacks he has launched on Washington and its allies over the past year as relations deteriorated to what many analysts deem a post-Cold War low.

Putin's more conciliatory tone could signal his hope to use the two leaders' personal chemistry to put uneasy ties between Moscow and Washington on firmer footing.

The summit will start on Saturday with a social dinner followed by formal talks and a news conference on Sunday.

They still face a deep divide on key issues.

NATO leaders rebuffed Bush's call to put Georgia and Ukraine on an immediate path to membership, a move some Europeans feared would have deeply antagonised Russia.

But Moscow made clear its concern about the alliance's ultimate decision - a promise to the two former Soviet republics that they would eventually be allowed in.

Putin also made no secret of Moscow's anger at NATO's endorsement of Bush's push for a missile defence system, which Russia sees as a threat to its security despite U.S. insistence it is meant to deter countries like Iran.

But Putin also expressed appreciation that Bush was listening to Russia's security concerns and looking for ways their countries could cooperate.

After the talks in Bucharest, Bush flew to Zagreb on Friday to help celebrate Croatia's invitation to join NATO.

Bush was due to deliver a speech to the Croatian people on Saturday in the capital's historic St. Mark's Square, in the company of the presidents of neighbours Albania and Macedonia.

Croatia and Albania received formal membership invitations at the summit but Greece vetoed an invitation to Macedonia because of their long-running dispute over its name - the same as Greece's northern province, home of Alexander the Great.

In talks with Croatia's President Stjepan Mesic, Bush reaffirmed his call for a resolution of the Macedonia impasse, which has raised fears of instability in the Balkans.