US President George W. Bush and his Russian counterpart Vladimir Putin failed to overcome their differences on missile defence at their final summit in south Russia Sunday.

However, the Russian leader said the talks at his residence in Sochi were generally positive, and that he was "cautiously optimistic" that the dispute, which has proved a major stumbling block in relations between Moscow and Washington, will be resolved.

The meeting between the Russian and US presidents, who will leave office next month and next January respectively, produced a "strategic framework" on future relations between the countries, encompassing areas ranging from trade to counter-terrorism to defence.

Summing up their seven-year relationship as presidents, the US leader said: We worked very hard over the past years to find areas where we can work together, and I think we've done a pretty good job of it... It's been a remarkable relationship."

Putin told the joint news conference: "I won't hide the fact that one of the most difficult issues was and remains American missile defence in Europe... I want to be understood correctly: there has been no change in our fundamental attitude to the American plans."

Bush said: "The Russian side has made clear that it does not agree with the decision to establish sites in Poland and the Czech Republic and reiterated its proposed alternative."

Bush also met in Sochi with Russian president-elect Dmitry Medvedev, who is set to take over in the Kremlin May 7 when Putin steps down.

The U.S. leader called Medvedev a "straightforward fellow", and said he looked forward to working with him when he assumes office. Their next meeting is likely to be at the G8 summit in Japan July 7-July 9, Bush said.