China and several ASEAN states have conflicting and overlapping claims in the South China Sea, but not all the Southeast Asian nations agree on how to handle them.
U.S. officials want the summit to produce a statement calling for China to follow international law and handle disputes peacefully.
"We will be continuing to work with our ASEAN partners on a potential statement that we might issue together," White House national security adviser Susan Rice told reporters on Monday.
"We obviously have issued such statements in the past with ASEAN, and in it we consistently underscore our shared commitment to a peaceful resolution of disputes, freedom of commerce and navigation, the rule of law, and the necessity of disputes being resolved through peaceful, legal means," she said.
Obama is expected to address the issue during a news conference at the conclusion of the summit around 1:30 PST.
Though China dominated the summit, the White House emphasized non-China related aspects, such as strengthening commercial ties. The chief executives of IBM, Microsoft and Cisco were brought into Monday’s private sessions with the leaders to help make the point.
"The potential for deepening our economic engagement is tremendous," U.S. Commerce Secretary Penny Pritzker said. Monday’s discussions with the "private sector partners" ranged from the need for capital to creating an entrepreneurial culture in Asia that is prepared to tolerate business failure.
But even business leaders were watching the South China Sea issue.
"What keeps us up at night is that one of the big tension areas is the South China Sea," said Alexander Feldman, president of the U.S. ASEAN Business Council.
"We would like as a business community to see those differences and overlapping claims be addressed in a way that is done though discussion rather than military confrontation," he said.