Former US presidential candidate John McCain has said the West must intervene to stop the bloodshed in Syria.
Senator McCain, who challenged Barack Obama for the presidency in 2008, said the United States and other Western powers should be "ashamed" of their decision not to take stronger action against the regime of Bashar Al-Assad.
Speaking to BBC Radio 4's World at One programme on Wednesday, McCain said he was "puzzled" by comments from Western governments that they did not want to risk "militarising" the conflict, arguing it already had been militarised.
"Russian arms shipments continue to come in, the Iranians are on the ground assisting them, so they have tanks and artillery supplied by Russians and others against people who demonstrate peacefully," he said. "That's not a fair fight."
"It is clear the doctrine of Assad is to murder and torture and rape in order to intimidate and perhaps beat the population into submission, it's not random acts of violence, it's a campaign of terror," he said.
"Now we are up to estimates of up to well over 10,000 Syrians have been slaughtered. The question is how many more have to die at hands of bloody dictator before we intervene"
McCain told the BBC that the president needed to do more to challenge the regime.
"When was the last time you heard the president of the United States speak up on behalf of these people who are being slaughtered?" he asked. "It's disgraceful, we should be ashamed."
"It took a massacre in Srebrenica [in Bosnia] before we intervened in the '90s," he said. "Massacres are taking place as we speak."
"We can look back on this as we did in Bosnia and Kosovo with pride, or we can look back on it with shame as we did in Rwanda."
McCain said the West should use its airpower to help create a "sanctuary" in Syria in which opposition groups could re-group, train and get medical attention.
"You can think of all kinds of reason not to act, the facts on the ground are indisputable, Bashar Assad is slaughtering and massacring his own people, torture, rape and murder are matters of doctrine," he said.
"You can think of a thousand reasons not to intervene, to sit by and watch it happen, I am not prepared to do that," he added.
McCain also rejected the suggestion that the Syrian regime's air defences would prove a stern test for Western air forces.
"I think if the sanctuary were declared and the Syrians were told they would be punished by air power, we could protect that sanctuary," he said.
"We spent $800bn of taxpayers money here in the US on defence, and if we can't take out the Syrian air defences then American tax dollars have been frittered away."