Secretary of State John Kerry says the United States has to change what he calls Syrian President Bashar al-Assad's "calculation" about his situation.
Kerry on Wednesday said Assad has not yet realized that it is inevitable he will be thrown out of power.
The secretary of state told reporters at the State Department he has a good sense of what he might propose to get Assad to change his perception. But Kerry said there are a lot of people who have to be consulted before any announcements are made.
Kerry on Wednesday hosted Jordanian Foreign Minister Nasser Judeh, whose country's economy is under stress by helping to care for 300,000 Syrian refugees. Judeh said he did not want to put a timeline for President Assad's ouster, and again called for talks and a political transition.
The United Nations says the nearly two-year-old uprising against the authoritarian Assad government has killed close to 70,000 people. Most of the dead are civilians.
The head of the Russian government arms export agency, Anatoly Isaikin, says Russia is continuing to sell weapons to Syria because there are no sanctions against such sales and its contracts are legally binding.
But Isaikin says Russia is only selling defensive weapons to Syria -- nothing that can be used to attack people.
Kerry said Wednesday that he is hopeful Russia and the United States can find more common ground on Syria.
Russia, a long-time Syrian ally, has vetoed U.N. Security Council sanctions on Syria, angering the United States.