A four-day ceasefire between the Syrian government and Kurdish forces has expired, with pressure mounting on the Kurdish-led Syrian Democratic Forces (SDF) to fully integrate its fighters into the Syrian army.

The ceasefire ended at 8 pm (17:00 GMT) on Saturday, with no official announcement of an extension from either side as Syrian troops and SDF forces massed near the front lines around a last cluster of Kurdish-held cities in the northeast.

Syrian Information Minister Hamza al-Mustafa said on X that his government was “now considering its next options”.

Earlier, Syria’s foreign ministry denied that government forces had reached an agreement with the SDF on extending the deadline of the ceasefire deal reached earlier this week.

“There is no truth to what is being circulated regarding the extension of the deadline with the SDF,” the Syrian Arab News Agency (SANA) quoted the ministry as saying.

As the Saturday deadline approached, SDF forces reinforced their defensive positions in the cities of Qamishli, Hasakeh and Kobane for a possible fight, Kurdish security sources told news agency Reuters.

The standoff comes amid rising tensions over the last year, as President Ahmed al-Sharaa vowed to bring all of the country under state control after his forces toppled longtime ruler Bashar al-Assad in 2024.

But Kurdish authorities who have run autonomous civilian and military institutions in the northeast for the past decade have resisted, leading Syrian troops to launch an offensive this month after a year-end deadline for the merger passed with little progress.

Syrian military officials told Reuters they were readying forces for a fight. Reuters reported seeing army vehicles and buses ‌of fighters arriving near Hasakah, where SDF forces have also bolstered positions.

Future being decided ‘one day, one hour at a time’

The Syrian army and the SDF agreed to a four-day ceasefire on Tuesday, after Kurdish fighters relinquished swaths of territory to government forces, which also sent reinforcements to a Kurdish stronghold in the northeast.

Government troops have seized expanses of northern and eastern territory ⁠in the last two weeks from the SDF in a rapid turn of events that has consolidated al-Sharaa’s rule.

Al-Sharaa’s ​forces were approaching a last cluster of Kurdish-held cities in the northeast earlier this week when he abruptly announced a ‍ceasefire, giving the SDF until Saturday night to come up with a plan to integrate with Syria’s army.

They brought key oil fields, hydroelectric dams and some facilities holding ISIL (ISIS) fighters and affiliated civilians under government control.

The al-Aqtan prison in Raqqa province, which holds thousands of ISIL fighters, is now under the government’s control.

Al Jazeera’s Bernard Smith, reporting from al-Hol, said the Syrian army had taken hold of the camp housing tens of thousands of suspected ISIL members and that no escapes had been reported.

“There was a limbo period on January 20, when the SDF pulled out, and the camp was left unguarded until the Syrian army came back later that evening,” Smith said, adding that government forces were now “fully in control”.

Despite hope for a negotiated resolution, both sides have ramped up ​military preparations.

Meanwhile, the United States military has been transferring hundreds of detained ISIL fighters from Syrian prisons ‌across the border into Iraq.

Al Jazeera’s Zein Basravi, reporting from Raqqa, on Saturday said “the future of Syria is being decided one day, one hour at a time”.

“The ceasefire seems to be what everyone is talking about,” he said. “The immediate goal is to make sure that the ceasefire remains, if only for a little while longer.”