All eyes will be on how Mr Putin and Mr Bush get on

This has especially been the case with UK Prime Minister Tony Blair and the German Chancellor, Gerhard Schroeder. Mr Blair took the unusual step of making an unofficial visit to St Petersburg while Mr Putin was still acting Russian president.

Their trip to the opera was taken as a loud endorsement of Mr Putin's candidacy for the job. And as families, the Putins and the Schroeders have already paid mutual visits to each other's homes.

Mr Putin chooses his international friends carefully, though. He speaks fluent German, and passable English, meaning that even if official interpreters are in attendance, with Mr Schroeder and Mr Blair he doesn't actually need them.

Clinton in the cold

And as someone who can expect to be leader of his country for some years hence, he wants relationships which will have some long-term significance.

Hence, he saw little point in making pals with Bill Clinton, when he knew that they would overlap as leaders for less than a year.

Missile defence is a major sticking point

If only for the language and longevity reasons, he may now consider it worth trying to establish a relationship with Mr Bush.

This personal element has been a feature of relationships between the top men in Moscow and Washington ever since the first signs of a thaw in the Cold War in the late 1980s.

After six years without a meeting of the top two, the Soviet leader Mikhail Gorbachev and the US President Ronald Reagan met on neutral territory in Geneva in November 1985.

Talks were held in an informal setting, earning it the nickname of 'the fireside summit'.

Reagan and Gorbachev

After another meeting on neutral ground - Reykjavik - in 1986, the two leaders played home and away on the next two occasions. Mr Reagan was the host in December 1987, Mr Gorbachev in May 1988.

These summits played a major role in improving bilateral relations and cutting nuclear arsenals.

If Mr Reagan's meetings with Mr Gorbachev started with the fireside summit, George Bush Senior's relationship with the Soviet leader had a less cosy start.

Bill Clinton and Boris Yeltsin seemd to share a warm relationship

The venue for their first encounter, in December 1989, was a US warship anchored off Malta in the Mediterranean Sea. Turbulent weather led the meeting to be dubbed 'the seasick summit'.

Subsequent changes - from Mr Gorbachev to Boris Yeltsin in Moscow, and from Mr Bush to Mr Clinton in Washington - saw no disruption to the now smooth progress of Russo-US summits.

'Pancake'

And under Mr Yeltsin and Mr Clinton, the personal element of the relationship seemed to take on a new significance. The two men roared with laughter at one post-summit press conference when Mr Yeltsin insulted the press corps.

And Mr Clinton didn't seem to mind one bit when Mr Yeltsin stumbled over the US President's name, referring to him as "Blin Clinton". Blin means 'pancake' in Russian.

What the hell, thought Blin. Such culinary references are, after all, a traditional element of the US presidency.

Didn't John F Kennedy, on a visit to Berlin, declare: "Ich bin ein Berliner," which, according to urban myth, literally means "I am a doughnut."