International mediators could be forced to step in after Thailand and Cambodia on Monday failed to solve a spat over an ancient Hindu temple that has inflamed nationalist sentiment in both countries and sparked a military stand-off.

The impasse in talks in Thailand between defence officials from the two countries coincided with a meeting of foreign ministers from the Association of South East Asian Nations in Singapore. The 10-nation Asean urged both countries to show “utmost caution and restraint” and offered to help resolve the dispute. Still, in a sign that the regional group is in no hurry to test its abilities as a regional peace broker, Surin Pitsuwan, secretary-general, told the Financial Times on Monday night that the two countries “should find their own solution and I think that they are determined to find one”.