Upcoming talks between Cambodia and Thailand are unlikely to resolve the military standoff at their disputed border near an ancient temple, a Cambodian commander said on Sunday.

More than 500 Thai troops and well over 1,000 Cambodian soldiers are stationed around a small Buddhist pagoda on the slope of a mountain leading to the ruins of 11th century Preah Vihear temple. Officials from both countries plan to meet Monday to try and resolve the standoff.

"We have very little hope about the negotiations," said Brigadier Chea Keo, commander of Cambodian forces in the area, on day six of the confrontation.

"We have only a little hope because the new Thai government has written a letter to our prime minister saying that the land they are stationed on belongs to them," he told reporters.

"We're on high alert," he added.

Cambodia has also sent letters about the standoff to the United Nations, government spokesman Khieu Kanharith told AFP.

"Cambodia's permanent mission at the United Nations has sent two letters. One to the Security Council and another one to the chief of the UN General Assembly in order to draw the attention about the situation that is happening in Cambodia," Khieu Kanharith said.

"After the Monday negotiations we will decide what is the next step," he added.

The mood among Cambodians was tense Friday evening after word spread of a letter from Thai Prime Minister Samak Sundaravej to his Cambodian counterpart Hun Sen saying the addition of Cambodian troops had caused the situation to "deteriorate".

The standoff nearly erupted into violence late Thursday, when witnesses said troops twice pointed their guns at each other during 10 tense minutes at the pagoda after 50 Cambodian troops entered the compound to protect food supplies for dozens of monks.

The confrontation began after three Thai protesters were arrested for jumping a fence to reach the temple on Tuesday.

The World Court ruled in 1962 that Preah Vihear belongs to Cambodia. But the most accessible entrance to the Khmer ruins lies in Thailand and 4.6 square kilometres (1.8 square miles) of the surrounding land remains in dispute.