"The U.S. already flunked the test and that should be a wakeup call," a former senior U.S. State Department official told Newsweek.

The rapid announcement of a ceasefire, with Malaysia as mediator, offered a welcome pause. Yet the dust had barely settled before the shadow of great power rivalry reemerged.

U.S. Secretary of State Marco Rubio said State Department officials were in Malaysia to assist peace efforts as Cambodia and Thailand were scheduled to begin talks there on Monday in hopes for a ceasefire.