Turkish President Abdullah Gul said on Thursday Russia and Iran would soon realize they had little choice but to join international diplomatic efforts for the removal of Syrian President Bashar Assad.
He acknowledged, however, the divisions in the Syrian opposition and its lack of preparedness to take power, saying it must create a structure that embraces all segments of society.
"This transformation will no doubt take time."
Turkey has been in the forefront of fostering the Syrian opposition since abandoning its long-time ally Assad over his violent crackdown on protests. The opposition Syrian National Council meets in Istanbul and the 'Free Syrian Army' operates from Turkish soil on the Syrian border.
Turkey and Western and Arab allies were angered by Russia's vetoing, along with China, of a United Nations Security Council resolution condemning Assad's use of force, which has intensified in past days with a siege against the city of Homs.
"We have to wait and see how long Russia will be able to take upon itself the burden of this regime," he told Reuters in an interview. "In my opinion, it won't be very long.
"In the time of the Cold War, such things happened in a very closed environment. However, today developments take place in the open.
"I think in time Russia will see its support has been abused by the Syrian regime. They will recognise this fact when they see the heavy weapons being used against the people in Syria. That is not very tolerable, not even for Russia," he said.
Russia has continued to supply arms to Syria as protests have grown, with the formation of rebel military units, into something approaching civil war.
Defeated Syrian rebels pulled out of the city of Homs on Thursday after a 26-day army bombardment, but fighting continues across the country. Sources say arms are being brought into Syria for the opposition forces by non-government parties.
Russia and China moved a step towards joining international action on Thursday when they joined other Security Council members in expressing "deep disappointment" that Damascus had refused to allow U.N. humanitarian aid chief Valerie Amos into the country.
In vetoing the resolution, Russia had argued that both sides of Syria's conflict should be condemned for the violence, not just Assad's government.
The Turkish presidency is not executive and most power in the country rests with the prime minister, Tayyip Erdogan. However, Gul commands great personal influence and plays a central role in foreign policy.
Gul said Ankara was talking to Iran, a close ally of Assad, in an effort to persuade it to accept the inevitable and back diplomatic action against Assad.
"Even Iran doesn't have the power to make water run uphill - And if the worse scenario were to come true, it is not possible that Iran could not feel any responsibility for that. It will be responsible."
He said Russian and Iran should be persuaded by the international community and countries of the region to persuade the Syrian government to accept reality and stop the crackdown. He cited the 'Yemeni Model' as the most reasonable option as a way out for Assad.
In Yemen, president Ali Abdullah Saleh stepped aside, under pressure from Gulf Arab states, with guarantees of protection to allow an election for a new leader.
Gul has warned in the past of the danger of violence in Syria fuelling sectarian conflict that could envelop the entire Muslim Middle East.
"It's a trap in the region, and similar incidents happened in the Middle Ages in Europe. The Middle East should not repeat these mistakes.
"We know that the danger is there, but awareness is also there."
In Syria, any new administration must find ways of accommodating Sunni Muslims and Christians as well as the Alawites who have been the bedrock of Assad's rule.
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