More than 70 foreign ministers from Western and Arab nations backing the Syrian uprising are gathering in Istanbul Sunday for talks aimed at pressuring Damascus to implement an immediate cease-fire and urging the opposition to unify its scattered ranks.

U.S. Secretary of State Hillary Clinton and other officials attending the “Friends of Syria” meeting are expected to insist that Syrian President Bashar al-Assad abide by the peace plan proposed by U.N.-Arab League envoy Kofi Annan.

President Assad, whose foreign ministry has declared the revolt crushed, has said he accepts Mr. Annan's six-point proposal. But his comments have been treated with skepticism by Western and Arab governments as fighting on the ground continues.

Syria's political opposition, which remains divided, has not yet formally endorsed the Annan plan, and rebel fighters say they will not put down their arms until government troops and heavy weapons are withdrawn from populated areas.

On Saturday, Clinton attended a “strategic forum” between the United States and the six-nation Gulf Cooperation Council in Saudi Arabia to discuss bringing an end to Syria's crackdown and countering the growing threat of Iran.

The U.S. remains opposed to arming Syria's rebels, like some Gulf states have proposed, and is instead working to unify the country's splintered opposition and find ways to get humanitarian aid into the country.

Ahead of Sunday's meeting, Turkish Foreign Minister Ahmet Davutoglu said the Annan plan is the “minimum” of what Syria must do “urgently and without delay.”

Meanwhile, the London-based Syrian Observatory for Human Rights told VOA that government shelling and clashes between security forces and protesters left 25 people dead Saturday.

The United Nations says more than 9,000 people have been killed since unrest in Syria began more than a year ago.

In a letter to the U.N. Friday, Syria said acts by “armed terrorist groups” had led to the deaths of more than 6,100 people in Syria since the start of the uprising.