China will come under the most concerted diplomatic pressure yet to rein in its assertive moves in the disputed South China Sea when the United States uses a regional security meeting this weekend to rally support for a freeze on provocative acts.
The push by U.S. Secretary of State John Kerry at the ASEAN Regional Forum marks a step up in Washington's involvement in the dispute, which has frayed regional ties as China acts more forcefully on its sweeping sovereignty claims.
Kerry arrives in Myanmar's capital Naypyidaw on Saturday, joining top diplomats from China, Russia, Japan, India, Australia, the European Union and Southeast Asia among others in Asia's highest-profile gathering so far this year. Foreign ministers of the 10-member Association of Southeast Asian Nations (ASEAN) begin talks on Friday.
Beijing rejects U.S. involvement in the dispute and has already dismissed proposals from Washington and Manila for a freeze on actions such as land reclamation and construction on disputed islands and reefs.
"The secretary is not looking for a showdown. This is not a superpower battle," said a senior U.S. State Department official, stressing that Kerry would call on all claimants to show restraint, not just China.
Washington, however, has singled China out.
Daniel Russel, the State Department's senior diplomat for the East Asia region, said in a speech on July 28 that public evidence indicated China's upgrading of outposts on small land features in the South China Sea was "far outpacing" similar work other claimants were doing.
On Thursday, Chinese state media said China planned to build lighthouses on five islands in the South China Sea. At least two of the islands - Drummond Island and Pyramid Rock - are in the Paracel Islands, which are also claimed by Vietnam and Taiwan.
The unusually strong U.S. stance will add pressure on Beijing to address growing regional concerns and could encourage some ASEAN nations to push for faster progress on a maritime code aimed at reducing tensions. China accuses the United States of emboldening claimants such as the Philippines and Vietnam with its military "pivot" back to Asia.
"The Americans have decided that based, not on what China is saying, but what it is doing, they had to lift their game," said Ernest Bower, a Southeast Asia expert at the Center for Strategic and International Studies in Washington.
"The call for the freeze should be seen as a new level of engagement and diplomacy on this issue by the Americans."
China claims 90 percent of the South China Sea, which is believed to contain oil and gas deposits and has rich fishing grounds. Brunei, Malaysia, the Philippines, Vietnam and Taiwan also lay claim to parts of the sea, where about $5 trillion in ship-borne trade passes every year.
Tensions spiked in May when China parked a giant oil rig in waters claimed by Vietnam. Relations between China and U.S. ally the Philippines have also cooled in recent years over the disputed sea territories.
The rancour has split ASEAN, with several states including some of the claimants reluctant to antagonise Asia's economic giant. ASEAN's biggest economy, Indonesia, backs the proposals for a freeze and will ask others to specify which actions they would cease, its Foreign Minister Marty Natalegawa said.
"What I will be seeking at the ASEAN meeting in Myanmar is for us to be able to spell out what we actually mean when we say self-restraint," he told reporters on Tuesday.
A draft of the planned ASEAN foreign ministers' joint statement seen by Reuters includes a call for a freeze on "destabilizing actions" but that reference could be removed or watered down. Smaller nations such as Cambodia, Laos and host Myanmar have deep economic and political ties with Beijing, and may be receptive to Chinese complaints of external interference.
ASEAN and China signed a trust-building agreement in 2002, committing to exercise "self-restraint" in activities that would escalate disputes, such as occupying islands and reefs or building on them. Most claimants have flouted those guidelines.
The Philippines accused China in May of reclaiming land on the disputed Johnson South Reef and said it appeared to be building an airstrip. Taiwan is building a $100 million port next to an airstrip on the lone island it occupies in the disputed region.
As well as Johnson South Reef, a senior Philippine navy official told Reuters that China was continuing land reclamation work on Gaven, Cuarteron and Eldad Reefs in the disputed Spratlys chain. He also said Manila had a four-year plan - currently shelved by budget constraints - to build helipads on two shoals, install radars and sensors in other areas and to build a port and extend an airstrip on Pag-asa island.
The official declined to be identified because he was not authorised to speak on the South China Sea issue. China said this week it can build whatever it wants on its islands in the waterway.