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

Thailand and Cambodia exchanged fire along their disputed border for a second day on Friday, officials from both countries said, with more than a dozen people reported killed and more than 135,000 civilians evacuated.

The U.N. Security Council planned to hold an emergency meeting in New York on the crisis, while Malaysia, which chairs a regional bloc that includes both countries, called for an end to hostilities and offered to mediate.