David Cameron will hold talks with the Russian president, Vladimir Putin, at Downing Street on Thursday as he tries to persuade the Russians to take a tougher line on the crisis in Syria.
Cameron will have to test Putin's willingness to accept a political solution in Syria that involves the removal of the Assad regime.
After the talks the pair will go to see an Olympic judo match. Putin who has not visited Britain for nine years, is trying to play down the significance of the meeting. A black belt in judo, his aides say he is coming to watch the sport rather than indulge in high level diplomacy.
Diplomatic efforts will be further complicated by Russia's frosty relations with Britain, with tensions over espionage, human rights, trade deals and the presence of a community of outspoken Russian political exiles in Britain.
The two countries are still at odds over the 2006 death from radiation poisoning in London of Kremlin critic Alexander Litvinenko, whose widow lives in Britain. Putin's treatment of Russian dissidents is not likely to be raised in what will be fraught enough discussions.
Cameron will press for serious diplomatic discussions against the sporting backdrop and possible Russian success in the judo. Cameron said: "We will be at the judo so it may be a bit off-putting." The focus of the talks could be reduced to trade if Putin signals no interest in discussing Syria.
As the honorary president of the International Judo Federation, the sport's governing body, Putin will be concentrating on the judo mat, as much as a map of Damascus. Surrounded by Russian athletes and flag-waving fans, the Russian leader will probably be keen to play up to his strong man image.
The men's 100kg and women's 78kg judo competitions are on during the day, with the two finals scheduled to take place at around 4pm. One Russian each is in contention in both the men's and women's competitions.
Diplomacy over Syria has reached a kind of stalemate in the wake of the collapse of the peace plan proposed by the former UN secretary general Kofi Annan.
Britain and Russia are both permanent members of the UN security council and the Russians, often with Chinese backing, have steadfastly opposed any form of UN resolution that could be seen to be supporting military intervention, or even military-backed humanitarian corridors.
At least three resolutions have been blocked by the Russians, and the British in turn were instrumental in preventing a Russian-originated arms shipment from reaching Syria.
Britain has said that Assad's departure has to be the basis of any agreement, but has hinted that the Syrian leader could avoid any charge of international war crimes if he left office voluntarily.
The apparent offensive in the main Syrian northern town of Aleppo does not suggest that the Syrian regime is on the brink of collapse or in the mood to surrender.
Britain has proposed an international conference on the future of Syria, but its efforts have been hamstrung by Russian insistence on the attendance of the Iranians, and by divisions within the Syrian opposition.
A one-time judo champion in his native St Petersburg, then called Leningrad, Putin has always promoted his muscular side – stalking tigers, flying a fighter jet and riding a horse bare-chested in Siberia.
"For us it's a great honour and it gives us encouragement and we of course try not let ourselves, the country and him down when we compete," said Russian fighter Ivan Nifontov, who took bronze in the men's 81kg category on Tuesday.
During a visit to Northern Ireland Cameron met one of the seven young athletes who lit the cauldron during the opening ceremony of the games last Friday.
• This article was amended on 2 August 2012 because it referred to "a visit to Northern Island". This has been corrected.
