It gave the Kurdish-led Syrian Democratic Forces four days to agree on integrating into the central state, which their main ally, the United States, urged them to accept.
Syria's military seized swathes of territory from the SDF in the country's northeast.
The lightning government advances in recent days and the apparent withdrawal of US support for the continued holding of territory by the SDF represent the biggest change of control in the country since rebels ousted Bashar al-Assad 13 months ago.
US envoy Tom Barrack in a social media post described the offer of integration into the central Syrian state with citizenship rights, cultural protections and political participation as the "greatest opportunity" the Kurds have.
He added that the original purpose of the SDF, which the US had supported as its main local ally battling the Islamic State group, had largely expired and that the US had no long-term interest in retaining its presence in Syria.
The United States is monitoring with "grave concern" developments in Syria, a White House official said, and urged all relevant parties to continue negotiating in "good faith".
"We urge all parties to exercise maximum restraint, avoid actions that could further escalate tensions, and prioritise the protection of civilians across all minority groups," the White House official said.
The SDF said it accepted a ceasefire agreement with the Syrian government and that it would not engage in any military action unless attacked.
A Syrian government statement said it had reached an understanding with the SDF for it to devise an integration plan for Hasakah province or risk state forces entering two SDF-controlled cities.
The government announced a four-day ceasefire starting on Tuesday evening and said it had asked the SDF to submit the name of a candidate to take the role of assistant to the defence minister in Damascus as part of the integration.
Northeast Syria, wedged between Turkey and Iraq, is home to both Kurds and Arabs and was largely overrun by IS fighters a decade ago before the SDF drove them back with air support from a US-led coalition.
However, advances by the SDF's main component, the Kurdish YPG force, were concerning to US ally Turkey, which regarded it as an offshoot of the PKK group that had waged a years-long insurgency inside Turkey.
Since Assad was overthrown in December 2024, Syria has been led by former Islamist rebel leader Ahmed al-Sharaa, who has emerged as a close ally of Turkey.
The ceasefire announcement came after SDF forces earlier on Tuesday abandoned their posts guarding a camp housing thousands of people affiliated with IS - a move that the Syrian military said allowed detainees to escape.
The al-Hol camp in north-eastern Syria houses mainly women and children who are family members of IS members or accused of being otherwise affiliated with the group.
The SDF exit followed heavy fighting in the area around the camp.
The camp is officially not a prison but is often described as such by residents, who are not allowed to leave voluntarily.
Kurdish officials have warned that losing control of such camps could enable a resurgence of the group and plunge parts of Syria into renewed violence and instability.
The SDF has overseen several facilities housing people linked to the group across northeastern Syria.
It accused factions allied with the Syrian government of carrying out attacks on prisons holding the militants.
Violence began flaring earlier this year after government troops, backed by Arab tribal fighters, advanced into areas that had been under SDF control for years.
with DPA and Reuters
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