WASHINGTON - U.S. Secretary of State John Kerry has told Chinese officials that Washington will launch countermeasures if Beijing takes further provocative acts in the South China Sea, U.S. diplomatic sources said Thursday.

If Beijing unilaterally declares an air defense identification zone over the disputed waters, for example, "It will force our hand," Kerry was quoted by one of the sources as saying during the U.S.-China Strategic and Economic Dialogue on June 5-7 in Beijing.

Kerry stopped short of saying what kind of countermeasures he has in mind. But he appears to have signaled actions such as strengthening U.S. freedom of navigation operations and the deployment of U.S. military units in the South China Sea.

Kerry also demanded that China abide by a ruling that a U.N.-backed arbitral tribunal will hand down on July 12 regarding the legitimacy of Beijing's claims to almost the whole South China Sea, according to the sources.

"The world is watching" China's response to the ruling to be issued by the Permanent Court of Arbitration in The Hague, Kerry was quoted by the source as saying.

The Philippines brought the arbitration case to the court, arguing China's claims to most of the South China Sea violate the U.N. Convention on the Law of the Sea. Many experts believe the coming ruling will be unfavorable for China.

During the talks in Beijing, Kerry expressed displeasure about China's lobbying to member states of the Association of Southeast Asian Nations not to support the arbitration process.

"We know what you are doing -- dividing ASEAN," Kerry was quoted by another source as saying.

A Chinese official, however, said, "We are not bound by the UNCLOS," the source said.

China has said it will not accept arbitration on the South China Sea and repeated its preference to negotiate bilaterally with other claimants such as the Philippines and Vietnam in a perceived attempt to overwhelm them with its economic might.

The United States is considering expanding the Navy's surveillance activity in the South China Sea as Beijing has stepped up island construction and militarization of outposts in the disputed waters in an apparent attempt to unilaterally alter the status quo there.

Washington is closely watching whether Beijing will take further provocative measures such as unilaterally declaring an ADIZ over the South China Sea and reclaiming Scarborough Shoal, which Manila claims as its territory.

Separately, the United States has informed China that it will refrain from taking specific actions on the South China Sea before Beijing hosts a summit of the Group of 20 major developed and developing nations in September, according to a diplomatic source.

The move signals Washington's push on Beijing to exercise restraint ahead of planned talks between President Barack Obama and President Xi Jinping on the sidelines of the Sept. 4-5 summit in Hangzhou, eastern China.

==Kyodo