David Cameron and Vladimir Putin will hold talks on the Syrian civil war at a summit in Downing Street.
The British Prime Minister and Russian President will discuss the ongoing crisis during Mr Putin’s first visit to the capital in nine years.
Mr Cameron is likely to raise Russia's continual blocking of a United Nations Security Council resolution, designed to increase the pressure on President Bashar al Assad.
Mr Assad's government troop are currently engagement in a bloody conflict with rebel fighters, which had led to at least 19,000 deaths.
The talks come two weeks after Russia and China vetoed the latest UN attempt to end the bloodshed, and as Syrian government forces continue their battle to regain full control of the northern city of Aleppo.
UN relief co-ordinator Baroness Amos said the lack of a resolution to establish a safe zone in Syria was hampering attempts to help civilians caught up in fighting.
She said a resolution would be needed to establish a secure corridor for the delivery of aid supplies or a safe zone for people fleeing violence in the 17-month uprising.
"It is extremely worrying, and it is not just Aleppo. A couple of nights ago we had renewed conflict in parts of Damascus too," she said.
But President Assad has hailed his army's military action against what he termed "terrorist criminal gangs", saying their battle will determine the fate of the country.
Mr Cameron is also under pressure to raise the 2006 death of Kremlin critic Alexander Litvinenko , who was allegedly poisoned with Polonium 210 by a Russian agent, with Mr Putin.
Mr Litvinenko's widow, Marina, condemned the Russian leader's London visit, saying she was "dismayed".
"Mr Putin's agents killed my husband, a British citizen, in the centre of the British capital and contaminated hundreds of innocent people with radioactive poison," she added.
After the meeting, President Putin will go to the ExCel centre to watch the Olympic judo competition. He is a black belt in the martial art.
