Meanwhile, Russia, long friendly to the al-Assad regime, is looking past the Syrian government for a solution.
Russia's president declared Thursday that its goal is to end the bloody conflict in Syria, not help the nation's embattled president cling to power at all costs.
"We are advocating the solution that would prevent the collapse of the region and the continuous civil war," Russian President Vladimir Putin said in Moscow. "Not retain al-Assad and his regime."
To do that, he said, talks between opposing sides are crucial.
"First, people should negotiate, agree on how their participation would be guaranteed ... not first destroy everything and then try to negotiate," Putin said.
Al-Assad has not visited Moscow much in his tenure, and Russia does not have "special economic relations" with Syria, according to Putin.
Russia is "not concerned" about al-Assad's fate, he said.
"We understand what's going on (in Syria). We know that this family has been in power for 40 years," he said.
U.S. officials have accused Russia and China of blocking tough efforts against al-Assad by vetoing U.N. Security Council resolutions against the Syrian government.