WASHINGTON (Reuters) - The White House on Friday urged Chinese President Xi Jinping to extend his pledge not to militarize the disputed Spratly Islands to encompass all of the South China Sea.

Chinese dredging vessels are purportedly seen in the waters around Mischief Reef in the disputed Spratly Islands in this still image from video taken by a P-8A Poseidon surveillance aircraft provided by the United States Navy May 21, 2015. REUTERS/U.S. Navy/Handout via Reuters ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. REUTERS IS UNABLE TO INDEPENDENTLY VERIFY THE AUTHENTICITY, CONTENT, LOCATION OR DATE OF THIS IMAGE. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS

Dan Kritenbrink, President Barack Obama’s top Asia advisor, issued the call at the end of a week in which China and the United States have sparred over Chinese deployment of missiles, fighter planes and radar on islands in the contested strategic waterway.

Xi had pledged during a U.S. state visit last September not to militarize the Spratly archipelago, which is claimed by Manila and Beijing, but U.S. officials have since said they see military intent in China’s building of air strips and installation of radar there.

Friction has increased over China’s recent deployment of surface-to-air missiles and fighter jets to Woody Island in the disputed Paracel chain. It has been under Chinese control for more than 40 years but is also claimed by Taiwan and Vietnam.

“We think it would be good if that non-militarization pledge, if he (Xi) would extend that across the South China Sea,” Kritenbrink told a conference at the Center for Strategic and International Studies. “We’re going to encourage our Chinese friends and other countries in the region to refrain from taking steps that raise tensions.”

Admiral Harry Harris, head of the U.S. Navy’s Pacific Command, said this week China was “changing the operational landscape” in the South China Sea and the United States would increase freedom-of-navigations patrols. His congressional testimony coincided with a U.S. visit by Chinese Foreign Minister Wang Yi.

China says its military facilities in the South China Sea are “legal and appropriate,” and on Tuesday, in a reference to U.S. patrols, Wang said Beijing hoped not to see more close reconnaissance or dispatch of missile destroyers or bombers.

Kritenbrink also reiterated that China should respect an international court ruling expected later this year on its dispute with the Philippines over the South China Sea.

China, which claims virtually all the South China Sea, is facing an arbitration case filed by Manila. Beijing rejects the authority of the Permanent Court of Arbitration in the Hague, even though it has ratified the U.N. Convention on the Law of the Sea on which the case is based.

“When that ruling comes out, it will be binding on both parties,” Kritenbrink said. “That will be an important moment that all of us in the region should focus on.”