Former international development secretary Andrew Mitchell has called for war crime prosecutions in Syria to be put on hold to preserve the country's fragile ceasefire.
The chairman of the all-party parliamentary group on Syria also called US foreign policy in the country "a total failure", adding that incoming president Donald Trump could be "a silver lining" in efforts to end the conflict.
A ceasefire brokered by Russia and Turkey survived its first day on Friday, a major mark of progress after six years of fighting.
Asked on LBC Radio whether war crimes charges should be brought against Syria's president Bashar Assad, Mr Mitchell said they should be "held for now while we try and get on with having a ceasefire that works".
He added: "The reach of international justice, which has been gravely damaged by what the Russians have done, should certainly not be forgotten in due time. But for now, I don't think that is the first priority.
"The first priority is to get the ceasefire to hold, and for talks between all the different parties to take place."
The Tory MP for Sutton Coldfield said war crimes had been committed on all sides in the Syrian conflict, and the priority was for the international community to work with Russia and Turkey towards fresh negotiations for a peaceful solution.
He added: "That is the one silver lining to all of this, in that the Russians, President Putin, has made clear that he will work with the Americans, but once there's a new president."
Asked if Barack Obama's foreign policy had failed in the region, Mr Mitchell said: "Absolutely. There's no question that it's been a total failure, and worse than a failure, because having said that he would take action if those red lines were crossed, the failure to do so meant that everyone knew that America was not going to intervene and was a busted flush on that.
"There's a chance to reset the dial when President Trump takes over in a few days time now, and I hope that will lead to a constructive relationship."