Secretary of State John Kerry still is speaking sporadically with Russian, Turkish and Arab foreign ministers about cease-fire efforts, and there are occasional consultations with the opposition.
But less than two weeks before Donald Trump's presidency begins, the Obama administration no longer is even claiming to play the leading part in the peace mediation that it spearheaded unsuccessfully for years. Formal contacts with Russia and others in Geneva, the main meeting point for the U.S.-led diplomacy, have ended.
Leadership has been ceded to Russia and, to a lesser degree, Turkey and Iran.
After helping Syria's military oust the remaining rebels from the city of Aleppo last month, Moscow has cast itself as the would-be peacemaker. It clinched a new truce without Washington's help and announced Friday that it was starting to draw down its forces in the region.
Russian envoys also are organizing the first talks between the Syrian government and opposition in nearly a year. The discussions are set for later in January in Astana, Kazakhstan.
"We still are at the proverbial table," State Department spokesman John Kirby said Friday. "We may not be at the table in Astana, we may not be at the table in Moscow, I understand that. But it's not like we are walking away from Syria."
He added later: "We aren't connected to this piece of it. It's not like we're pulling out from the whole puzzle."
With no indication about how the incoming Trump administration intends to proceed on Syria, U.S. diplomats are wary of engaging in any new initiatives that would require a sustained American role. As a result, the Obama administration is ambivalent about attending, even in an observer role, the proposed peace meeting. Turkey has told the U.S. its presence would be acceptable, American officials said, but Washington has yet to make a decision.
The diminution of the American role could have drawbacks.
Obama demanded almost six years ago that Syrian President Bashar Assad leave power and allow for a democratic transition. But Obama's reticence to plunge the United States into another Mideast war meant the U.S. never had the capability to shape such an outcome. Its increasingly marginal role in recent months means it could have even less capacity to help shape Syria's future and safeguard vital American interests, such as Israel's security and fighting the Islamic State group.
On the other hand, Obama hands the baton to Trump without any large-scale military or diplomatic engagement in Syria. Obama never wanted to own the conflict, which has killed up to a half-million people and prompted millions to flee as refugees. On Saturday, at least 43 people were killed when a car bomb ripped through the center of a busy commercial district of a rebel-held Syrian town along the Turkish border, activists and rescue workers said.
Obama's reticence to intervene in the war at least means Trump will have flexibility, which Obama didn't have in inheriting the Iraq and Afghanistan wars.
In a farewell news conference Thursday, Kerry insisted the administration hadn't given up on Syria and that he hoped the warring sides could get to "real negotiations" on a peace agreement.
But some officials were frustrated by the administration essentially withdrawing from the process. For example, Kerry hasn't spoken to Russian Foreign Minister Sergey Lavrov since Dec. 27. Their discussions occurred almost daily at some points last year.
Russia, which backs the Syrian government, and Turkey, a strong supporter of Syria's moderate opposition, brokered the current shaky cease-fire, which came into effect on Dec. 30. The truce has mostly held but not altogether halted fighting; the government and opposition have blamed each other for violations.
The truce doesn't include areas in Syria controlled by IS.
The U.S. is pressing on with its effort in that campaign, and Trump and his national security advisers have said it will be a top priority for them.
The Obama administration has an undisclosed number of special operations troops, presumably about 200 to 250, in Syria. They are advising and assisting what the Americans call the Syrian Democratic Forces, which is comprised of Syrian Kurds and Arabs. Some of the Americans are embedded with the SDF in northern Syria.