US President, Barack Obama has promised a "vigorous investigation" for the use of chemical weapons in Syria, which if found could be a "game-changer".
Speaking at the White House, Obama said:
"Horrific as it is when mortars are being fired on civilians and people are being indiscriminately killed, to use potential weapons of mass destruction on civilian populations crosses another line with respect to international norms and international law.
"All of us, not just the United States, but around the world, have to recognise how we cannot stand by and permit the systematic use of weapons like chemical weapons on civilian populations."
Meanwhile, British Prime Minister David Cameron told the BBC he worried that there may be failure to act on the part of the West because of the trauma from Iraq.
"I choose my words carefully, but what I see does look very much like a war crime is being committed in our world, at this time, by the Syrian government."
"I would want to reassure people and say the lessons of Iraq have been learned.
"There are proper processes in place to try and make sure that what people say is properly backed up by the information.
"If anything, I would argue that because people are so worried about what happened in Iraq, it's actually quite important now to come forward - as the Americans have done and I think [US President] Barack Obama has done it in a very clear and measured way."