US President Donald Trump has said the prime ministers of Thailand and Cambodia will halt fighting "effective this evening".

Trump made the announcement after telephone conversations with the two leaders following deadly border clashes in recent days which have left at least 20 people dead and half a million displaced.

Neither Thai PM Anutin Charnvirakul nor his Cambodian counterpart Hun Manet has commented.

However, after his call with Trump earlier, Charnvirakul told a news conference that a ceasefire would only come about if "Cambodia will cease fire, withdraw its troops, remove all landmines it has planted".

In a post on his social media platform Truth Social, Trump said both leaders "have agreed to CEASE all shooting effective this evening, and go back to the original Peace Accord made with me.