China, Philippines Face a Re-test of Recently Improved Relations
The sea is rich in fisheries and may have extensive reserves of undersea fossil fuel. Brunei, Malaysia, Taiwan and Vietnam also claim all or parts of it.
A ministerial-level Philippine delegation is in Beijing through Tuesday this week to meet Chinese Vice Premier Wang Yang for talks about investment deals and Duterte's role as head of ASEAN in 2017. In another Beijing-friendly move, ASEAN has not placed the South China Sea on its agenda this year.
Philippine-China relations will get stickier if the United States gets involved and the U.S. government has shown tentative signs of tapping Manila for a stronger military relationship under Trump.
The U.S. government is a long-standing counterweight to Chinese military power in Asia and recently an ally of smaller Asian countries faced with Beijing's maritime expansion. Washington seeks to protect marine shipping lanes and a network of pro-U.S. Asia Pacific allies.
Better U.S. relations under Trump?
Duterte has railed against the United States since taking office, saying the former Philippine colonizer and contractual defense ally demands too much from his country. Duterte vented particularly after Washington criticized his campaign the against drug trade that has included the suspected extrajudicial killings of 5,000 to 6,000 people.
But he and Trump talked by phone in December, an upbeat conversation with Trump lauding the Philippine anti-drug effort and earning praise from Duterte.
"Locally, Duterte has attempted to portray Trump as being very friendly and supportive of his administration, and to change his tune about the U.S. under Trump," said Jay Batongbacal, director of the Institute for Maritime Affairs and Law of the Sea at University of the Philippines.
The Philippines would find it hard to finesse a showdown between China and the United States over Chinese occupation in the sea, said Carl Baker, director of programs at the think tank Pacific Forum CSIS in Honolulu.
Trump's nominee for secretary of State, Rex Tillerson, advocated at his early January U.S. Senate confirmation hearing that China be stopped from occupying more disputed islets in the sea. China may have built military installations in the Spratlys as preparation for Trump's presidency, Carl Thayer, emeritus professor of politics at the University of New South Wales in Australia.
Duterte probably would not let Trump position troops in the Philippines to resist China, Thayer said.
"The longer term is quite different. The buildup of the U.S. military is going to take years. That's not going to happen immediately," Thayer said. "And it seems clear to me that Trump is really after market access and a resolution of the so-called currency manipulation issue with China."