"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 latest flare-up started on Thursday, with intense fighting spreading across multiple border areas. Early Saturday, Thailand’s navy joined the army in repelling what it described as incursions by Cambodian troops at three points in eastern Trat province.

The countries continued to trade fire on Friday, and at least 16 people are reported to have been killed.

Thailand favours bilateral negotiation rather than third-party mediation to resolve its military conflict with Cambodia, two Thai officials said, as fighting along their disputed border continued unabated.

Of course, trouble at the 508-mile (817 km) shared border is nothing new. For over a century, Thailand and Cambodia have contested sovereignty at various undemarcated points in the thick jungle punctuated with culturally-significant temples albeit with scant strategic or economic value.

Thailand bombed Cambodia with F-16 fighter jets on Thursday, as relations between the two countries imploded following clashes on a disputed border near the Emerald Triangle.

Tensions have bubbled between the two neighbors for months, flaring on Thursday as Cambodia and Thailand exchanged fire.

Four dead as Tropical Storm Wipha tears through Thailand, China and into Vietnam - Heavy rain in China's eastern province of Shandong kills two people and leaves 10 missing