VIENTIANE, Laos (AP) — U.S. Secretary of State Antony Blinken told Southeast Asian leaders Friday that the U.S. is concerned about China's “increasingly dangerous and unlawful” activities in the disputed South China Sea during an annual summit meeting, and pledged the U.S. will continue to uphold freedom of navigation in the vital sea trade route.

The 10-member Association of Southeast Asian Nations’ meeting with Blinken followed a series of violent confrontations at sea between China and ASEAN members Philippines and Vietnam, which have fueled concerns that China’s increasingly assertive actions in the waterways could spiral into a full-scale conflict.

China, which claims almost the entire sea, has overlapping claims with ASEAN members Vietnam, the Philippines, Malaysia and Brunei, as well as Taiwan. About a third of global trade transits through the sea, which is also rich in fishing stocks, gas and oil.

Beijing has refused to recognize a 2016 international arbitration ruling by a U.N.-affiliated court in the Hague that invalidated its expansive claims, and has built up and militarized islands it controls.

“We are very concerned about China’s increasingly dangerous and unlawful activities in the South China Sea which have injured people, harm vessels from ASEAN nations and contradict commitments to peaceful resolutions of disputes,” said Blinken, who is filling in for President Joe Biden, in his opening speech at the U.S.-ASEAN summit. “The United States will continue to support freedom of navigation, and freedom of overflight in the Indo Pacific.”

The U.S. has no claims in the South China Sea, but has deployed navy ships and fighter jets to patrol the waters in a challenge to China’s claims.

Chinese and Philippine vessels have clashed repeatedly this year, and Vietnam said last week that Chinese forces assaulted its fishermen in the disputed sea. China has also sent patrol vessels to areas that Indonesia and Malaysia claim as exclusive economic zones.

The U.S. has warned repeatedly that it’s obligated to defend the Philippines — its oldest treaty ally in Asia — if Filipino forces, ships or aircraft come under armed attack, including in the South China Sea.

Philippine President Ferdinand Marcos Jr. complained to summit leaders on Thursday that his country “continues to be subject to harassment and intimidation” by China. He said it was “regrettable that the overall situation in the South China Sea remains tense and unchanged” due to China’s actions, which he said violated international law. He has called for more urgency in ASEAN-China negotiations on a code of conduct to govern the South China Sea.

Singaporean leader Lawrence Wong earlier this week warned of "real risks of an accident spiraling into conflict” if the sea dispute isn't addressed.

Malaysia, who takes over the rotating ASEAN chair next year, is expected to push to accelerate talks on the code of conduct. Officials have agreed to try and complete the code by 2026, but talks have been hampered by sticky issues including disagreements over whether the pact should be binding.

Chinese Premier Li Qiang was defiant during talks on Thursday. He called South China Sea a “shared home” but repeated China’s assertion that it was merely protecting its sovereign rights, officials said. Li also blamed meddling by “external forces” who sought to “introduce bloc confrontation and geopolitical conflicts into Asia.” Li didn’t name the foreign forces, but China has previously warned the U.S. not to meddle in the region’s territorial disputes.

In another firm message to China, Blinken said the U.S. believed “it is also important to maintain our shared commitment to protect stability across the Taiwan Strait.” China claims the self-ruled island of Taiwan as its own territory and bristles at other countries’ patrolling the body of water separating it from the island.

Blinken also attended an 18-nation East Asia Summit, along with the Chinese premier, Russian Foreign Minister Sergei Lavrov, and leaders from Japan, South Korea, India, Australia and New Zealand.

ASEAN has treaded carefully on the sea dispute with China, which is the bloc's largest trading partner and its third largest investor. It hasn't marred trade relations, with the two sides focusing on expanding a free trade area covering a market of 2 billion people.

Blinken said the annual ASEAN summit talks were a platform to address other shared challenges including the civil war in Myanmar, North Korea’s “destabilizing behavior” and Russia’s war aggression in Ukraine. He said the U.S. remained the top foreign investor in the region, and aims to strengthen its partnership with ASEAN.