Ignoring President Xi Jinpings calls for the 21-nation meeting to focus on economic ties, Obama demanded "bold steps to lower tensions" between China and its smaller South East Asian neighbours.
In comments clearly targeted at Beijing, Obama said those steps should include "pledging to halt further reclamation, new construction, and militarisation".
Smaller regional nations, including summit host the Philippines, are rattled by Chinas increasing assertiveness in the strategic waterway.
These actions have included a spate of island building on disputed reefs and shoals, and many Asian nations are looking to Washington for support.
During his visit to Manila, Obama has been keen to offer that support, announcing the US would transfer two ships to the Philippine navy, boosting significantly Manilas capability to patrol the disputed Spratly Islands.
Obama has also stressed "iron-clad" US treaty obligations to defend the Philippines -- and other allies -- and vowed to boost military ties through new defence cooperation agreements.
But wary of drawing the United States or its allies into direct conflict with China, Obama also stressed the need to settle disputes under the rule of law.
"Disputes need to be resolved peacefully," said Obama, backing the Philippines decision to seek UN arbitration in several disputes with China.
China has so far refused to recognise the panels authority.(*)
Editor: Heru Purwanto
Copyright © ANTARA 2015
