PHNOM PENH - US President Barack Obama is set to wade into the troubled waters of Asia's maritime disputes at a regional summit next week, with allies hoping for support in their efforts to contain China.
Obama, on his first overseas trip since his re-election, will arrive in the Cambodian capital from Myanmar on Monday for the 18-nation East Asia Summit that observers expect will be dominated by a raft of territorial rows.
The two days of annual talks will be preceded on Sunday by a meeting of leaders from the 10-member Association of Southeast Asian Nations, which have struggled to forge a united stance on China's claims to the West Philippine Sea (South China Sea).
"Maritime security issues will once again be front and centre," said Ian Storey, a regional security analyst with the Institute of Southeast Asian Studies in Singapore.
"Beijing's renewed assertiveness over its sovereignty claims... has unnerved many countries in the Asia-Pacific region. They will be looking to the United States for strategic reassurance."
The Philippines and Vietnam have this year expressed growing concern at what they perceive as increasingly aggressive tactics by China in staking its claims to the South China Sea, which is home to shipping lanes vital to global trade.
China insists it has sovereign rights to nearly all of the waters, while ASEAN members the Philippines, Vietnam, Brunei and Malaysia, as well as Taiwan, have competing claims to parts of the sea.
With Washington keen to assert itself as a Pacific power and counter a rising China, Obama is expected to be "quite vocal" on the sea rows, said Pavin Chachavalpongpun of Kyoto University's Centre for Southeast Asian Studies.
Obama is likely to reiterate that the United States has a fundamental interest in freedom of navigation in the sea, while urging ASEAN and China to agree on a code of conduct for the area, according to Storey.
ASEAN comprises Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand and Vietnam -- a grouping of nearly 600 million people from disparate economic and political systems.
The bloc had hoped to negotiate a code of conduct this year governing behavior in the disputed waters, but progress stalled when ASEAN foreign ministers fell out over the maritime issue at a meeting in Phnom Penh in July.
ASEAN chair Cambodia, a close China ally, refused to allow Hanoi and Manila to mention specific run-ins with Beijing over the sea, preventing the group from issuing a joint communique for the first time in its 45-year history.
"Cambodia will be keen to avoid a repeat of the July fiasco", said Storey, but he warned that Phnom Penh "won't support any moves on the South China Sea by its ASEAN partners that would annoy China".
Storey and Pavin agreed there was little chance of a code of conduct being successfully negotiated at the upcoming talks, but there would be an effort to show parties were looking for diplomatic solutions.
A row between China and Japan over rival claims to islands in the East China Sea, which has severely shaken diplomatic and trade ties between the Asian powers this year, is also expected to cast a shadow over next week's talks.
In yet another territorial dispute, Japan is at loggerheads with fellow US ally South Korea, whose President Lee Myung-Bak angered Tokyo with a surprise visit to a disputed island chain in the sea between the two countries in August.
Lee and Japanese Prime Minister Yoshihiko Noda are planning to hold their first formal talks since the spat erupted on the sidelines of next week's meetings, Kyodo News agency said this week, citing Japanese government sources.
But traditional trilateral talks between the leaders of China, Japan and South Korea are not expected to occur because of the tensions.
Away from the maritime conflicts, ASEAN leaders may turn their attention to recent communal clashes in western Myanmar that have left dozens dead and prompted an exodus of "boat people" to neighboring countries.
On the economic front, ASEAN members are set to launch negotiations over a giant free trade zone with China, Japan, South Korea, India, Australia and New Zealand.
The 16 nations account for roughly half the global population and around a third of the world's annual gross domestic product.