Thailand and Cambodia have accused each other of new attacks as border clashes continue for a third day, leaving at least 33 people dead and over 168,000 displaced as international pressure mounts on both sides to reach a ceasefire.

"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 have bickered for decades over jurisdiction of various undemarcated points along their 817 km (508 mile) land border, with ownership of the ancient Hindu temples Ta Moan Thom and the 11th century Preah Vihear central to the disputes.