David Cameron insisted he had "learned the lessons of Iraq" as world leaders at the G8 summit in Northern Ireland set out an agreed blueprint for the future of Syria.
But the British Prime Minister was again warned not to consider arming the Syrian rebels by President Vladimir Putin, who compared them to the killers of Drummer Lee Rigby.
Cameron and President Barack Obama persuaded Putin to agree to plans for a transitional government that could eventually replace the Assad regime, after intensive private discussions.
The Prime Minister appealed directly to supporters of the Syrian dictator to turn against him, promising that they could have a role in a future Syrian government. They should "know in their hearts" that the Assad regime was doomed, he said.
The Prime Minister heralded the deal agreed on the final day of the G8 summit in Northern Ireland as a "strong statement" that will pave the way for a Syrian peace conference.