The United States' top diplomat promised on Wednesday that Washington will not take sides in South China Sea disputes and called for China and the Philippines to exercise restraint and build confidence.

Experts said the milder tone being voiced by both Washington and Manila serves overall interests and is more conducive to regional stability, but Beijing should be cautious of future moves by the two countries and of possible tricks.

US Secretary of State John Kerry said in Manila that Washington is not picking sides on the competing sovereignty claims in the South China Sea.