BEIRUT — The first attempt by the Trump administration to cooperate with Russia on an international crisis got underway on Sunday, with the implementation of a cease-fire in southwestern Syria that appeared to be widely holding.

If the truce can be maintained, it could open the door to deeper cooperation between the United States and Russia on ways to quell the violence and to progress on other cease-fire deals being pressed elsewhere in Syria.

The guns fell silent well ahead of a noon deadline, residents in the cease-fire zone said, lending hope that it would stop the violence for at least a while and save lives.

The agreement to work on a cease-fire in Syria was the first publicized achievementof the meeting on Friday between Trump and Russian President Vladimir Putin. Details remain vague, however, and it is unclear whether the agreement will lead to cooperation toward an enduring solution to Syria’s six-year-old war.

This cease-fire is being referred to by the two powers as a “de-escalation,” reflecting the modest expectations for success after several previous failed attempts by President Obama to work with Russia to end the fighting.