Thailand is threatening to resign its membership of the World Heritage Committee if it approves Cambodia's management plan for Preah Vihear temple.
The Bangkok Post reports Prime Minister Abhisit Vejjajiva has sent this strong message to the current meeting of the committee in Brazil.
Natural Resources and Environment Minister Suwit Khunkitti is heading the Thai delegation in Brasilia.
The Post quotes him as saying that the plan to manage the Hindu temple and surrounding areas included a square kilometre of the disputed land.
Mr Suwit told the prime minister he believed Cambodia has won the backing of several committee members for its plan.
Cambodia was asked to submit the plan for approval after the Hindu temple was listed as a world heritage site in 2008.