Already, the SNC is bristling, after Clinton said Wednesday that the Obama administration was suggesting names and organizations that should feature prominently in any new leadership to emerge from the conference.
"Only the people of Syria can decide who represents them and who doesn't. No one else has a say in that," said Abdelbaset Sieda, the SNC's outgoing president. He spoke in Istanbul on Saturday at a function aimed at raising funds for orphaned Syrian children.
Nuland said Friday that the United States is not "dictating" for the opposition.
"This is a matter of the U.S. and other friends of Syria, supporting the voices from inside Syria who are saying that the SNC has not, over the past year, used this time to really broaden itself," she said.
In a sign of the importance Washington is hanging on the Doha meeting, Nuland said the U.S. delegation has been upgraded and will now be led by Assistant Secretary of State for Near Eastern Affairs Elizabeth Jones.
The SNC itself called the Doha conference, and for the first four days it will hold talks on bringing other activists and representatives of Syria's various religious and ethnic groups under its own aegis.
One the last day, participants would discuss the Syrian National Initiative proposal.
The U.S.-backed initiative was put forward by Riad Seif, a veteran Syrian opposition figure who has emerged as a strong candidate to lead a transitional government in Syria.
U.S. officials say he is among hundreds of opposition figures that U.S. diplomats have been impressed with in discussions during the Syrian crisis. The 66-year-old Seif, who suffers from cancer, is a former reformist lawmaker and businessman who spent years in Syrian prisons before the uprising began and is widely seen as a charismatic figure who can help put the country back together again.
He was beaten up by security forces at a protest in October last year before he finally left the country, where he has been quietly working with various opposition groups.
"Syria is in desperate need of strong leadership that is cooperative and inclusive, a leadership that responds to the needs of the revolution and our steadfast people," Seif wrote in the proposed initiative. "This leadership framework will represent the revolution and its goals."
In addition to the leadership body, the proposal would establish a military council, a judicial committee and a transitional government to be made up of technocrats.
A number of opposition groups are staying away from the conference, including the National Coordination Body, a rival to the SNC, and the National Democratic Front headed by veteran opposition leader Michel Kilo.
They complain of being sidelined and describe the SNC as a group of dictators no worse than Assad.
"Nobody can build a house alone and then invite the others to stay in the servants' room," said Haitham Manna, a Paris-based veteran dissident who heads the National Coordination Body's external branch. He said any unilateral decision at Doha to form a transitional government will only serve to fragment the opposition even more.
Karam reported from Beirut. Associated Press writers Abdullah Rebhy in Doha, Qatar, Matthew Lee in Washington and Ayse Wieting in Istanbul contributed to this report.