The Arleigh-Burke class-guided missile destroyer USS Barry conducted operations in the South China Sea in 2020. [AFP]

The top diplomats of China and the US sparred on Saturday over the South China Sea, where Beijing is locked in a territorial dispute with US treaty ally the Philippines.

Secretary of State Antony Blinken and Chinese foreign minister Wang Yi met on the sidelines of a foreign ministers meeting of the Association of Southeast Asian Nations (ASEAN) in Laos.

The US hailed the meeting as "open and productive," after Blinken had criticised Beijing's "escalatory and unlawful actions" in the South China Sea.

Chinese and Filipino ships have clashed in the waterway, fuelling fears of a conflict that could drag in the US due to its mutual defence treaty with Manila.

The US should "refrain from fanning the flames, stirring up trouble and undermining stability at sea," Wang said at the meeting, according to a foreign ministry statement.

"The risks and challenges facing China-US relations are still rising," he said.

Blinken also raised "US concerns about provocative actions" by China, including a simulated blockade of Taiwan following the May inauguration of President Lai Ching-te.

China claims the democratic island as its territory and slammed Lai's inauguration speech as "confession of independence."

"Whenever the promoters of Taiwanese independence will make a provocation, we will respond with a countermeasure," Wang said, according to Beijing's foreign ministry.

During the meeting, which a State Department official said lasted one hour and twenty minutes, Blinken also raised US concerns over China's support for Russia as it wages war in Ukraine.

The two had had not arranged another meeting.

Stormy seas

Beijing claims the South China Sea -- through which trillions of dollars of trade passes annually -- almost in its entirety despite an international court ruling that its assertion has no legal basis.

A Filipino sailor lost a thumb in the latest June 17 confrontation when Chinese coast guard members wielding knives, sticks and an axe foiled a Philippine Navy resupply attempt.

On Saturday, Manila said it had successfully resupplied troops on the Second Thomas Shoal -- the focus of clashes in recent months -- under a deal agreed with Beijing.

According to a Chinese foreign ministry statement released later, Wang said the deal was a "temporary arrangement... to manage the situation," without giving details.

On Friday, Wang called on the Philippines to "honour its commitments" under the deal rather than "backtracking or creating complications", warning Beijing would "respond resolutely" to any violation.

Wang also warned the Philippines over deploying a US medium-range missile system on its soil, saying it would "create tension and confrontation in the region and trigger an arms race."

The US Army said in April it had deployed the Mid-Range Capability missile system in the northern Philippines for annual joint military exercises.

Philippines military officials later said the system would be removed from the country.

China, Russia talk security

Blinken's stop in Laos is part of a multi-nation Asia visit aimed at reinforcing regional ties in the face of Beijing's growing assertiveness, including in the South China Sea, and its deepening ties with Moscow.

Blinken arrived in Laos two days after the foreign ministers of China and Russia met with the 10-nation ASEAN bloc -- and each other on the sidelines of the meeting.

On Thursday, Wang met Russian foreign minister Sergei Lavrov in Vientiane and discussed "building a new security architecture for Eurasia", according to Moscow's foreign ministry.

The pair also agreed to jointly "counter any attempts by extra-regional forces to interfere in Southeast Asian affairs", it said.

China has a strong political and economic partnership with Russia, with NATO members labelling Beijing as a "key facilitator" of Moscow's involvement in the war in Ukraine.

Myanmar

A joint communique released by ASEAN on Saturday expressed the bloc's "deep concern over the escalation of conflicts" in member-state Myanmar.

The country has been ravaged by violence since the military seized power in 2021, sparking renewed fighting with established ethnic minority armed groups and dozens of newer "People's Defence Forces".

ASEAN has spearheaded so far unsuccessful diplomatic efforts to resolve the crisis, with a five-point peace plan agreed between the junta and the bloc now moribund.

The five-point consensus "remains our main reference to address the political crisis," the joint communique said.

Myanmar's junta has been banned from high-level ASEAN summits over its coup and crackdown on dissent, in which rights groups say it may have committed war crimes.

Two senior bureaucrats represented Myanmar at the Laos talks.