At a joint news conference in the Kremlin's vast, gilded St Andrew's Hall, the two leaders spoke of their resolve to put differences behind them and focus on cooperating to solve global problems such as the spread of nuclear weapons.

Both mentioned the issues that still divide them - Russia's opposition to Washington's plans for a missile defence shield in central Europe and US insistence on Georgia's territorial integrity - but stressed the positives in public.

Mr Obama praised Mr Medvedev as a 'straightforward, professional' leader who understood the interests of the Russian people and wanted to understand those of the United States, adding: 'We have resolved to reset US-Russia relations so that we can cooperate more effectively.'

At a signing ceremony, Mr Obama and Mr Medvedev, wearing identical dark suits, white shirts and red ties, pledged to finalise a treaty by the year-end to cut the number of deployed nuclear warheads on each side to 1,500-1,675 from levels above 2,200.

Mr Medvedev described their talks as 'very useful and open, businesslike conversations' and said they would aim to build a US-Russia relationship worthy of the 21st century.

Russia will allow 4,500 flights a year carrying US troops and weapons to the war in Afghanistan to cross its vast territory free of charge, a move hailed by the US side as showing Moscow's willingness to help in the war on the Taleban.

Other accords covered the resumption of US-Russia military cooperation, the creation of a new joint government commission, and an exchange of information on prisoners of war, according to texts released by officials.

Clouds remain on the horizon.

Senior Russian officials repeatedly emphasised in the run-up to the visit that Moscow would not sign an arms treaty later this year unless Mr Obama made concessions on US plans for an anti-missile system in Europe, a project hated by the Kremlin which fears it could threaten Russia's security.

The leaders played down those differences at the Kremlin, saying they had agreed a statement to continue to work together to evaluate global threats from ballistic missiles. -- REUTERS