UNITED NATIONS (AP) _ The U.N. Security Council unanimously adopted a resolution Monday demanding Syria's full cooperation with a U.N. investigation into the assassination of Lebanon's former prime minister and warning of possible ``further action'' if it doesn't.

The United States, France and Britain pressed for the resolution following last week's tough report by a U.N. investigating commission, which implicated top Syrian and Lebanese security officials in the Feb. 14 bombing that killed Rafik Hariri and 20 others. The report also accused Syria of not cooperating fully with the inquiry.

The three co-sponsors agreed to drop a direct threat of sanctions against Syria in order to get support from Russia and China, which opposed sanctions while the investigation is still under way. Nonetheless, the resolution was adopted under Chapter VII of the U.N. Charter, which is militarily enforceable.