Thailand and Cambodia’s leaders are due to meet for peace talks on Monday, as a festering territorial dispute along their shared frontier dragged into a fifth day of open combat. At least 35 people have been killed and more than 200,000 displaced since Thursday as the countries fight over a smattering of contested ancient temples.

"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 leaders of Cambodia and Thailand have agreed to meet to negotiate a ceasefire, according to a social media post by United States President Donald Trump on Saturday.

China has dismissed allegations that it was supplying weapons to Cambodia amid its ongoing border conflict with Thailand that has led to at least 33 people dying and hundreds of thousands displaced.

People on both sides of the border share a cultural heritage much older than modern nation-states, dating back to the ancient Khmer civilization.

Thailand and Cambodia exchanged heavy artillery fire for a second day on Friday as border fighting intensified and spread, while Cambodia's leader said Thailand had agreed to a Malaysian ceasefire proposal but then backed down.

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.