Speaking after he met British Prime Minister David Cameron in London, Rasmussen welcomed the recent US-Russian agreement under which the Assad regime says it will give up its poison gas stocks. (Agencies)
Damascus said earlier it was confident the UN Security Council will not adopt a resolution on its chemical weapons under Chapter VII, which could allow the use of force. But Rasmussen said, "I would expect the Syrian regime to fully comply with the demands of the international community and in the case of non-compliance we will need a very firm international response."
"I do believe that the credible threat of military action was the reason why diplomacy got a chance and I think in order to keep momentum in the diplomatic and political process the military option should still be on the table," he said.
The alliance chief said it was "crucial that the UN Security Council expeditiously adopts a firm resolution that can constitute the framework for a swift, secure and verifiable elimination of all chemical weapons in Syria".
Rasmussen said the use of chemical weapons "is a crime, is a violation of international law and those responsible must be held accountable". US President Barack Obama threatened military action against Syria following an August 21 chemical weapons attack on a Damascus suburb that allegedly killed hundreds of people, but held off after the US-Russian deal.
The United States, France and Britain want compulsory measures under Chapter VII of the UN Charter if Syria does not uphold the disarmament plan. But Russia, a key ally of Syrian President Bashar al-Assad, is firmly opposed to anything that could pave the way for the use of force.
Speaking after he met British Prime Minister David Cameron in London, Rasmussen welcomed the recent US-Russian agreement under which the Assad regime says it will give up its poison gas stocks.