Barack Obama becomes just the sixth US President in history to visit Moscow, seeking to open a new chapter in a relationship still haunted by the legacy and suspicions of the Cold War.

Allies in World War II when the joint aim of defeating Nazi Germany overcame deep ideological divisions, the US and Soviet Union became bitter nuclear-armed foes post war.

The collapse of Communism and the emergence of an independent Russia raised hopes of a new era of harmony but efforts to bury the past were mired by disputes on defence and the balance of power in the post-Soviet world.

The back-slapping bonhomie of the Boris n' Bill show under charismatic Presidents Mr Yeltsin and Mr Clinton - which once saw the Russian reduce his US partner to tears of laughter - failed to eliminate the lingering distrust.

And while George W. Bush famously professed to have sensed "the soul" of his ex-KGB counterpart Vladimir Putin, his presidential psychoanalysis did not foresee bruising disputes over missile defence and ex-Soviet states.

It is in this context that Mr Obama will meet youthful Kremlin chief Dmitry Medvedev and Mr Putin, now a strongman prime minister, with the aim of "resetting" relations after the turbulence of the Bush years.