Al-Assad has said he will not deal with opposition members influenced from the outside.
Russian Foreign Minister Sergey Lavrov said Saturday there was no alternative to U.N.-Arab League special envoy Kofi Annan's peace plan, despite mounting evidence that it's being violated daily.
"The situation looks more and more grim," Lavrov said. "For the first time since the beginning of this crisis, we see the question of foreign intervention. And our position remains unchanged. We will never agree to sanction the use of force in the U.N. Security Council."
He called foreign intervention a "dangerous game" and said it would have serious consequences in the entire region. He also blamed recent violence -- including reports of horrific massacres in Houla and Qubeir -- in part to opposition groups being supported by other nations.
Russia, along with China and four central Asian nations, has signed a joint declaration rejecting armed intervention in Syria and reiterating support for Annan's peace plan.
Amid the international talks, a humanitarian crisis looms within Syria, opposition groups say.
"Several doctors have been detained to prevent them from aiding the wounded amid a state of panic among residents due to the abuses regime forces are committing against the people there," the LCC said.
A doctor in the besieged city of Al Qusayr, near the Lebanese border, said he has to keep moving his makeshift hospital to prevent attack. Journalist Robert King documented the chaos in the hospital on video as medical staff rushed to save lives.
King said he has seen snipers targeting children.
CNN cannot independently confirm reports of casualties or violence in Syria, as the government has restricted access by international journalists.