China's positioning of a rig in disputed waters of the South China Sea raises questions about its territorial commitments, a senior U.S. diplomat said.

U.S. Secretary of State John Kerry is scheduled to meet with leaders from Southeast Asian nations this weekend. He's expected to press countries in the region to take steps to de-escalate crises tied to territorial claims in the South China Sea.

China National Petroleum Corp. announced it completed drilling and exploration activity in waters of the South China Sea disputed with Vietnam and pulled its rig out of the area last month.

Daniel Russel, the senior State Department diplomat in charge of regional affairs, said pulling the rig out of the area removed a source of tension, but raised "serious questions" about China's commitments in the region.

Russel said Kerry is expected to call for a regional code of conduct to help reduce tensions in the region.

Apart from the rig deployment, China has taken provocative actions in the South China Sea against most of its littoral neighbors.

China says it's operating within its maritime borders, though Vietnam said the rig's deployment is a violation of international laws.

The U.S. government has said it has no stance on who has sovereign claims to the territory in question, but views China as the aggressor.