The US has asked Thailand and Cambodia to "cease hostilities immediately" as border clashes extended for a third day, killing at least 10 people and displacing hundreds of thousands.
The two nations must follow de-escalatory measures outlined in a peace accord brokered by US President Donald Trump in October, Secretary of State Marco Rubio said.
Trump has also said that he would "make a phone call" to stop the fighting, which is the most serious escalation since clashes in July killed dozens of people.
Both countries have blamed each other for re-igniting the fighting, which has seen air strikes and exchanges of artillery fire.
The death toll over three days of hostilities stands at 10 - seven from Cambodia and three from Thailand. Thai officials said they evacuated more than 400,000 people, while Phnom Penh said 100,000 on the Cambodian side have been moved to shelters.
