UNITED NATIONS — France has taken the first steps toward proposing a Security Council resolution that would refer Syria to the International Criminal Court for the prosecution of war crimes, diplomats said Friday, an action long sought by rights advocates.

Although Russia might well veto such a resolution, the diplomats said, it could still embarrass the Kremlin, the Syrian government’s most important foreign supporter, at a time when the Russians already face isolation over the crisis in Ukraine. The diplomats also cautioned that such a resolution risked alienating the Russians, whose cooperation in pressuring the Syrian government is considered vital.

The diplomats spoke on the condition of anonymity because a draft of the resolution is still under negotiation.

Russia has vetoed three Security Council resolutions that would have imposed sanctions on the Syrian government for its conduct over the course of the conflict, now in its fourth year. But the French effort would be the first time that the 15-member council took action to hold suspected war criminals accountable. The council has the power to authorize the International Criminal Court in The Hague to prosecute, even though Syria is not a party to the treaty that created the court.