Western governments may have to "swallow" Russia's determination to prop up Bashar Assad's regime in order to defeat Islamic State (IS), a senior Conservative has said.
Britain and the United States "might have to live with" the Syrian dictator remaining in power, Crispin Blunt added.
The chairman of the Foreign Affairs Select Committee said the "bottom line" was defeating IS, also known as Isil, and suggested a vote on British intervention could wait because "we are pretty marginal in military terms".
Asked about the prospect of Assad continuing as president, Mr Blunt told BBC Radio 4's Today programme: "Yes, we might have to live with it.
"We need to be careful about not making the best option, which would be the removal of Assad and the defeat of Isil, not the enemy of the necessary objective of our policy, which is ending this civil war and the defeat of Isil.
"If we are faced with that rather difficult choice then we might have to swallow the fact that a UN Security Council permanent member, Russia, and their very important neighbour, Iran, are going to be prepared to commit the military resources and give Syria the overhead cover in the UN Security Council to enable the regime to survive."
Russia's military has carried out a second round of airstrikes in Syria but the action has further strained relations between Washington and Moscow amid reports that moderate opposition forces have been targeted rather than IS.
US secretary of state John Kerry warned Vladimir Putin that Russia must "not be engaged in any activities against anybody" other than IS.
Mr Putin is meeting French and German counterparts Francois Hollande and Angela Merkel in Paris to discuss the continuing crisis in Ukraine but the talks are set to be overshadowed by events in Syria.