“We are working hard to push everybody back to compliance. And we are cautiously optimistic that we can get there by Monday or Tuesday of next week,” Rubio told journalists.

Foreign ministers of the Southeast Asian bloc Asean are set to meet Monday in Kuala Lumpur, where they will discuss the crisis.

Rubio spoke Thursday by telephone with Thai foreign minister Sihasak Phuangketkeow and said the administration would hold further conversations over the weekend.

President Donald Trump had earlier this year claimed victory after he pressed for an earlier ceasefire, placing Thailand and Cambodia on a list of wars he said he solved.

“Both sides have made commitments in writing that they signed,” Rubio said.

“Those commitments today are not being kept as a result of both sides claiming grievances against one another, and so the work now is to bring them back to the table.”

He defended the administration’s record, saying that its diplomacy “actually did stop fighting”, although it has since resumed.

The conflict stems from a territorial dispute over the colonial-era demarcation of their 800km (500-mile) border and a smattering of ancient temple ruins situated on the frontier.

The renewed fighting this month has killed at least 21 people in Thailand and 18 in Cambodia, while displacing more than 800,000 people, officials said