Brig.-Gen. Manaf Tlas, one of the most senior defectors from President Bashar Assad's rule, said he would help unite Syria's fragmented opposition inside and outside the country to agree a roadmap for a transfer of power.
Tlas, speaking in a newspaper interview in the Saudi city of Jeddah, also said he was looking for support from Saudi Arabia and other powers.
"I am discussing with...people outside Syria to reach a consensus with those inside," Tlas told Thursday's edition of the Saudi newspaper Asharq al-Awsat.
"I left (Syria)...to try to help the best I can to unite the honorable people inside and outside Syria to set out a road map to get Syria out of this crisis".
Tlas, a former friend of Assad's who could play a role in any transition of power, said he "did not leave Syria to lead the transitional period".
"I realize this is a difficult phase... It's difficult for one person to bear the responsibility of such a phase," he said.
"A group (including opposition) from inside and outside Syria should cooperate to accomplish this phase."
The general, a Sunni Muslim member of Assad's mostly Alawite inner circle and a senior officer in the Republican Guards, defected earlier this month.
"I will cooperate with every honorable person who wants to rebuild Syria, be it the National Council or the (rebel) Free Syria Army," he said.
Tlas said it would be difficult to overthrow the president from within. "The structure and system of the regime makes a coup from inside very difficult," he said, adding he did not see a future for Assad in Syria.
Asked whether Assad was calling the shots in Syria, he said: "They are the decisions of the circle around him... He is not weak but there (are people) in the circle around him who played down the crisis to him, so he preferred to deal with it through a (security) framework".
Assad is seeking to crush a 16-month-old revolt against his rule in which at least 17,000 people have been killed and which is now being fought out in the country's two main cities.
Tlas said state institutions should be protected, in an apparent warning against a repeat in Syria of the US purge of Iraqi officials and state bodies after the 2003 invasion which plunged the country into years of anarchy.
"There are many people in the regime whose hands are not covered in blood and they should not be removed," he said. "We should preserve the national institutions in Syria and preserve the state and tackle only those who committed wrongs in handling the crisis."