Britain today warned President Bashar al-Assad that he did not have "unlimited time" to find a peaceful settlement with opposition protesters in Syria.
Attending the international "Friends of the Syrian People" conference in Istanbul, Foreign Secretary William Hague said the issue could return to the United Nations (UN) Security Council if current efforts to resolve the crisis fail.
The regime has said it accepts a peace plan by the UN-Arab League envoy Kofi Annan, but so far there has been little evidence that it is prepared to end its brutal crackdown on the opposition.
Mr Hague accused Assad of "stalling for time" and warned that if the issue does return to the Security Council, he may no longer be able to rely on the backing of Russia and China, who blocked a previous resolution calling for him to stand down.
"There isn't an unlimited period of time for this, for the Kofi Annan process to work before many of the nations here want us to go back to the UN Security Council - some of them will call for arming the opposition if there isn't progress made," he told BBC1's The Andrew Marr Show.
"What is now being put to them is a plan from Kofi Annan supported by the whole United Nations Security Council, and this is an important point, it's supported by Russia and by China as well as by the more obvious countries - the United States, the United Kingdom, France, the Arab League and so on.
"So, if the Assad regime fails to go along with this plan and doesn't start implementing this on the ground then they are in defiance not only of what we have said but of what Russia and China have supported as well, and that then may be a different situation at the UN Security Council from those we've faced over the last year."
Mr Hague reiterated his view that ultimately the regime could not survive and that Assad would have to go.
"One of the lessons of the Arab Spring is that if a dictatorial regime sets out to try to eliminate by force the desire for freedom and democracy of a very large part of their population, then they will fail, and that is why we remain convinced that this is a doomed regime," he said.