16:41 17 November 2015
David Cameron, who met earlier with Russia's President Vladimir Putin, has said that the Paris terror attacks "underlined the threat we all face."
He confirmed that while the gap between Russia and the West's position on Syria "has been enormous" "everyone now recognize the need for compromise."
French PM Manuel Valls said that the attacks, which left 129 people dead, were organised from Syria. He added that authorities believe new attacks are being planned in France and other European countries.
Russia has been carrying out air strikes in Syria in support of President Bashar al-Assad since September, saying it was targeting IS.
However, Mr Cameron said: "I've said Assad should go immediately, and we have to compromise and recognise there is going to have to be a transition," Mr Cameron said.
But he maintained "the fact that Assad can't play a role in the long-term government of Syria is not a political preference, but a political fact."
Both the British and Russian sides have emerged from these talks convinced to end the war in Syria to fight extremism.
Mr Cameron also said people should be "vigilant" against those who want to "change our way of life and destroy our way of life", and called for Britain to show "resolve" and "carry on with our lives."