The United States and China on Sunday applauded the leaders of Thailand and Cambodia after a second ceasefire was agreed to end months of border clashes that have killed dozens of people.

The day-old truce appeared to be holding as China, which has played a key mediator role, hosted talks with the warring nations in the southwestern province of Yunnan.

What did Trump say?

US President Donald Trump said he was pleased the conflict had come to a "rapid and very fair conclusion," adding on his Truth Social platform that Washington was "proud to help."

Ahead of his meeting on Sunday with President Volodymyr Zelenskyy to reach a peace deal to end Russia's war in Ukraine, the Republican went further, suggesting "perhaps the United States has become the REAL United Nations."

Trump often portrays himself as the one leader willing to take charge and resolve conflicts where the UN falls short, while critics argue that he is undermining international institutions.

The US, along with China and Malaysia, has been involved in mediation efforts to end the Thai-Cambodian conflict.

China hopes both sides can 'rebuild mutual trust'

As China prepared to host a two-day meeting with the warring parties on Sunday, Foreign Minister Wang Yi called the ceasefire "an important step towards restoring peace," adding that it was "in line with the shared expectations of countries in the region."

Wang told his Cambodian counterpart Prak Sokhonn that "both sides should proceed step by step to promote a comprehensive and lasting ceasefire" and "rebuild mutual trust."

The Chinese diplomat said that Beijing was willing to provide humanitarian aid to Cambodia to help those displaced in the border regions.

The first batch of Chinese aid, including food, tents and blankets, arrived in Cambodia on Sunday, Wang Wenbin, China's Ambassador to Cambodia, wrote on Facebook.

Thai-Cambodian diplomats praise China's input

Sokhonn expressed deep appreciation for China’s "vital role" in supporting the ceasefire, while his Thai counterpart, Sihasak Phuangketkeow, called for China to play more than a mediator role.

"Thailand ... wants China to play a constructive role in ensuring a sustainable ceasefire by sending such signals to Cambodia [against reviving the conflict]," he said.

The Chinese, Thai and Cambodian militaries were scheduled to join the talks in the southwestern Chinese province of Yunnan.

The three armed forces are due to discuss ways to consolidate the ceasefire, resume exchanges and build political trust between the two neighbors.

How did the Thai-Cambodian conflict break out?

The two countries have longstanding border disputes around ancient temple sites, which have flared up over the years.

The latest clashes erupted with the killing of a Cambodian soldier in May. The conflict escalated in July, before a first ceasefire was brokered by Malaysia, with support from the Trump administration.

The truce held until earlier this month, when what Bangkok describes as "freshly laid" landmines exploded, injuring several Thai soldiers. 

Rewewed heavy clashes erupted on December 8 with Thai airstrikes, artillery, rockets and ground operations spreading across multiple border points.

Both sides claimed self-defense and blamed the other for initiating violations.

First hours critical for ceasefire to hold

This year's violence killed dozens and displaced hundreds of thousands of people before both sides agreed to a second ceasefire on Saturday.

Announcing the deal, both countries pledged a halt to hostilities, a freeze on troop movements and to allow civilians living in border areas to return home.

The ceasefire will be observed for a period of 72 hours to ensure its implementation, the Thai Foreign Ministry said.

At the end of this period, Thailand has confirmed it will repatriate 18 Cambodian soldiers held as prisoners since July, fulfilling a major demand from the Cambodian side.

Edited by: Saim Dušan Inayatullah