“Nothing has changed,” said Iyad Shurbaji, a Syrian journalist in Damascus and a critic of the government. “Excessive violence has increased, tanks are still in the streets and not even one barricade has been removed.” He added: “The regime has no intention of carrying out the initiative. It is trying to buy time, betting on time to crush the uprising in attempt to create new facts on the ground, then negotiate from a strong position.”

Mediation has so far failed to blunt either the uprising or the crackdown, one of the most ferocious against any of the revolts that have swept the Arab world this year. The failure of neighboring Turkey was the most spectacular. After six hours of talks in August, including a one-on-one meeting between Turkey’s foreign minister and Mr. Assad, Turkish officials thought they had a deal, only to accuse Mr. Assad later of lying to them. Since then, Turkey has aggressively courted the exiled Syrian opposition.

Across the region, the Arab League effort, led by the Persian Gulf state of Qatar, was seen as perhaps the last opportunity to stave off more international pressure on Syria, especially at a time when more protesters have urged armed opposition against Mr. Assad’s government. Both sides suggested they were calling the other’s bluff.

“The truth will emerge, and it will become clear who really believes in dialogue and who fills the satellite TV screens with their screams calling for further killings, knowing nothing of dialogue,” Mustafa al-Miqdad wrote Thursday in Al Thawra newspaper, a mouthpiece of the Syrian government.

That sentiment was echoed across the divide. “This regime won’t start real dialogue,” said Warid Haddad, a Syrian opposition figure. “It’s still in a position of strength, dealing with people as if they are property.”

The Free Syrian Army, an armed group that claims to have organized defectors and carried out attacks on the military, said in a statement that it would halt its operations if the government did. Though its real abilities remain unclear, it warned that if the government persisted in the crackdown, “We will be obliged to protect the protesters.”