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.

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.

By Shoon Naing, Artorn Pookasook and Susan Heavey SISAKET, Thailand/WASHINGTON (Reuters) -U.S. President Donald Trump said on Saturday the leaders of Cambodia and Thailand had agreed to meet immediately to quickly work out a ceasefire,

Armed clashes on the remote, disputed border between Cambodia and Thailand have killed at least 12 people on Thursday, in a dramatic escalation of tensions that threatens to erupt into a broader conflict.

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

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.

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 is a major non-NATO ally of the U.S., while Cambodia is one of China's closest regional allies. The two countries began fighting after a recent dispute over landmines erupted into exchanges of fire on Thursday, July 24, with each side accusing the other of initiating the current hostilities.