The U.S. Secretary of State has expressed cautious optimism that Thailand and Cambodia might agree to a ceasefire by early next week as diplomatic efforts intensify to halt the renewed fighting along their shared border.

Marco Rubio told reporters Washington believes the two governments, under pressure from regional and international mediators, could agree to recommit to a cessation of hostilities by Monday or Tuesday, as special meetings of the Association of Southeast Asian Nations (ASEAN) approach.

Renewed clashes in December — after a fragile truce collapsed — have killed dozens and displaced more than half a million civilians, underscoring the urgency of restoring peace.

The remarks came amid parallel diplomatic engagement by both the United States and China, which have been encouraging de-escalation ahead of an ASEAN foreign ministers’ meeting scheduled for Monday in Kuala Lumpur.

Rubio’s comments reflect Washington’s ongoing role in seeking to revive a ceasefire framework after previous agreements brokered with ASEAN support faltered, as well as broader concern about the humanitarian impact and regional stability risks posed by the conflict.

China’s special envoy for Asian affairs also visited Phnom Penh to promote dialogue, reaffirming Beijing’s interest in supporting a peaceful settlement.

International efforts have emphasised the importance of ASEAN leadership and cooperative diplomacy, with the bloc’s current chair underscoring the need for a negotiated resolution that benefits both sides and prevents further civilian hardship.

The U.S. push for a ceasefire revival, if successful, would mark a significant step toward mitigating one of the most serious interstate disputes in Southeast Asia in recent years and reaffirm the role of multilateral engagement in resolving armed conflicts in the region.