The Trump administration is pressing eight European allies to commit by Friday to a U.S. proposal to stabilize northeastern Syria, U.S. officials said, setting a target meant to persuade reluctant partners to join Washington in the still-developing plan.

With U.S.-backed forces poised to seize the last remaining pocket of Islamic State resistance in Syria, U.S. officials have asked key allies, including France, the U.K. and Turkey, to remain part of the alliance and ensure the terror group doesn’t regain a foothold in northeastern Syria. The plan also is meant to avert a potential clash between the U.S.’s Kurdish allies there and Turkey, which considers the Syrian fighters terrorists.

Gen. Joseph Votel, the head of U.S. forces in the Middle East, on Thursday described the allied presence as essential to the U.S. effort in Syria, saying the absence of allies would make the mission more difficult and hurt momentum.

Under the latest Trump administration plans, U.S. forces would stay in the northern Syrian city of Manbij, continuing joint patrols with Turkish counterparts. A second group would be based east of the Euphrates River Valley as part of a safe zone between Turkey and Syria. Those U.S. forces also will help train and advise local forces so they can secure reclaimed territory once under Islamic State’s self-proclaimed caliphate, defense officials have said.

A third U.S. contingent would remain in the southern city of al Tanf, as part of a counter Islamic State campaign and a buffer against Iranian expansion in that region, military officials have said, but not part of the training and advising effort, a senior U.S. defense official said.