Thai and Cambodian leaders agreed to halt hostilities in their deadliest border conflict in more than a decade, after a push by the US and regional powers for a diplomatic resolution.

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

Long-festering tensions over border territory have escalated into armed conflict between Cambodia and Thailand, leading to dozens of deaths on both sides and displacing tens of thousands of people.

Livestock offices in Thailand's border provinces are offering safe space for animals whose owners have had to flee the fighting with Cambodia

Kasem Prunratanamala of CGS International warns that both Thailand and Cambodia stand to lose economically from the ensuing conflict, as Thailand’s trade surplus with Cambodia becomes at risk and Cambodia’s casino industry faces a hit as Thai visitor revenues dry up.

The Thai warning came as the U.S. expressed its grave concern about the most serious fighting in years between the Southeast Asian neighbors. The U.S. and China compete for influence in fast-growing Southeast Asia, and both have good relations with Thailand and Cambodia.