The 10-member Association of Southeast Asian Nations' meeting with Li followed recent violent confrontations at sea this year between China and ASEAN members Philippines and Vietnam that heightened unease over Beijing's increasingly assertive actions in the contested waters.
Philippine President Ferdinand Marcos Jr. said on Thursday 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.
"We continue to be subjected to harassment and intimidation," he told summit leaders.
He called for more urgency in ASEAN's negotiations with China for a code of conduct to govern the South China Sea.
He made clear to Li during talks Thursday that ASEAN-China cooperation cannot be separated from the sea dispute, according to an ASEAN official who declined to be named due to the sensitivity of the discussion.
Li responded by saying the South China Sea is "a shared home" and that China has an obligation to protect its sovereignty, the official said.
The Philippines, a longtime US ally, has been critical of other ASEAN countries for not doing more to get China to back away.
Malaysian Prime Minister Anwar Ibrahim, who will take over the rotating ASEAN chair next year, echoed the call for speedier negotiations.
Talks on the code of conduct have been ongoing for years, hampered by sticky issues including disagreements over whether the pact should be binding.
ASEAN reiterated the need to maintain peace and security in the strategic waterway, he said, according to Malaysian national news agency Bernama.
But Li said interference by foreign forces is creating conflicts within the region.
"We must realise that our development is also facing some unstable and uncertain factors. In particular, external forces frequently interfere and even try to introduce bloc confrontation and geopolitical conflicts into Asia," Li said during an ASEAN meeting with China, Japan and South Korea.
He called for more dialogue between countries to ensure disputes are resolved amicably.
Li didn't name the foreign forces but China has previously warned the US not to meddle in the region's territorial disputes.
US Secretary of State Antony Blinken has stepped in for US President Joe Biden at a summit in Laos. (AP PHOTO)
US Secretary of State Antony Blinken, who arrived in Vientiane on Thursday for the meetings, is expected to raise the issue of China's aggression in the sea, officials said.
The US has no claims but it has deployed Navy ships and fighter jets to patrol the waterway and promote freedom of navigation and overflight.
ASEAN members Vietnam, the Philippines, Malaysia and Brunei along with Taiwan have overlapping claims with China, which claims sovereignty over virtually all of the South China Sea.
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.
Aside from regional security issues, China's Li also emphasised Beijing and ASEAN's economic ties, saying intensifying trade relations and creating an "ultra large-scale market" are keys to economic prosperity amid rising trade protectionism.
ASEAN and China said they expect to conclude negotiations to upgrade their free trade pact next year.
Since the two sides signed the pact covering a market of two billion people in 2010, ASEAN's trade with China has leaped from $235.5 billion to $696.7 billion last year.
China is ASEAN's top trading partner and its third-largest source of foreign investment — a key reason why the bloc has been reluctant to criticise Chinese actions in the South China Sea.
The bloc is also holding individual talks with dialogue partners India, Australia, Canada, the US and the United Nations that will culminate in an East Asia Summit of 18 nations including Russia and New Zealand on Friday.
