As global powers prepared for an 11th-hour effort to revive the stalled peace effort in Syria, Kofi Annan, the special envoy and mediator who called the meeting, said Friday he was optimistic that the talks in Geneva would yield an acceptable result despite Russian calls for changes in his settlement ideas.

“I think we are going to have a good meeting” Saturday, Annan said as senior officials held preparatory talks in advance of the weekend encounter of foreign ministers, including US Secretary of State Hillary Rodham Clinton. “I am optimistic.”

But violence in Syria continued unabated with Syrian troops raining tank and artillery shells down on a rebellious suburb of Damascus, killing dozens of people during a particularly bloody week across the country.

It’s difficult to get an accurate death toll in tightly controlled Syria, where journalists and human rights groups are either banned or severely restricted. But two opposition groups that compile and document casualties reported the death of more than 125 civilians in fighting across the country on Thursday alone.

The British-based Syrian Observatory for Human Rights said Thursday’s toll included more than 60 soldiers. If confirmed, it would be one of the highest death tolls on a single day since the start of the uprising against President Bashar Al-Assad in March 2011.

The talks in Geneva would end “with an acceptable result,” Annan said, despite news reports suggesting that differences between Russia and other Western and Arab nations had raised new obstacles to an agreement.

Along with Clinton, Russian Foreign Minister Sergey V. Lavrov will attend, as well as the foreign ministers of Britain, China and France, the other permanent members of the Security Council. Also invited are emissaries from Iraq, Kuwait, Qatar, Turkey, the European Union and the Arab League, as well as Ban Ki-moon, the United Nations Secretary General.