Syrians should wage a campaign of civil disobedience to try to force President Bashar al-Assad from power, an exiled dissident said on Saturday at a meeting in Turkey aimed at forging a united opposition.

The opposition, divided between Islamists and liberals, is holding a "National Salvation Congress" to try to unite behind the goal of ending 41 years of Assad family rule, but is struggling to agree on whether to form a shadow government.

"I'm for anything that unifies the Syrian people and helps our people inside, and unifies our ranks in confronting this illegitimate repressive regime that has usurped power and human rights," opposition figure Wael al Hafez told the meeting in Istanbul.

"We want to raise the intensity of the peaceful confrontation by civil disobedience and to choke the regime economically and paralyse the state with the least damage."

The West has criticised Assad's crackdown on four months of protests demanding political freedoms. On Friday, his troops killed at least 32 civilians, including 23 in the capital Damascus.

U.S. Secretary of State Hillary Clinton, visiting Turkey, said Assad's repression of peaceful protests was "troubling".

"The brutality has to stop. There must be a legitimate, sincere effort with the opposition to try and make changes," she said in a televised interview with a group of young Turkish people at an Istanbul coffee shop on Saturday.

"I don't know whether that will happen or not. And none of us really have influence other than to say what we believe and encourage the changes that we hope for."

The opposition said the authorities had targeted a wedding hall in Damascus where it had planned to hold a simultaneous conference, connected by video link to the one in Istanbul.

"Several martyrs are fallen and others have been arrested," said Haitham al-Maleh, a venerable former judge who was among political prisoners released by Assad in March when the uprising began.

"The regime cannot deny us our freedoms. This state is for the Syrians, not Assad family's property," Maleh told the meeting of several hundred people.

Most of his audience have lived in exile for years, if not decades, and many have paid a heavy price for their dissent in previous crackdowns by the ruling Baath Party. Unlike other meetings in recent months in Turkey, some members of the opposition inside Syria managed to attend.

Assad's promises of reform have failed to quell the protests. Rights groups say some 1,400 civilians have been killed in the crackdown.

"My feeling is that the situation has reached a point of no return and the regime has also reached a point it cannot retreat after such a level of bloodshed," said Hassan Najar, an exiled Syrian originally from Aleppo, now based in Germany.

"After 41 years, the question is how can you bring together a fragmented opposition? We have had only four months and what has been achieved is a miracle."

But splits seemed to open over whether to form a government-in-waiting or wait to see how the uprising unfolds.

"People are demanding that the opposition speed up unifying its efforts so that people deal with it as a credible alternative," Ali Sadreddin Bayanouni, the former head of Syria's Muslim Brotherhood told Reuters.

Reuters