Updated Sept. 14, 2016 1:55 p.m. ET
MANILA—A rash of anti-American outbursts from Philippine President Rodrigo Dutertehas jolted U.S. allies in Asia, raising doubts about his commitment to a U.S.-led military alliance seeking to counter an increasingly assertive China—while leaving Beijing wary as well.
Allied governments from Washington to Tokyo to Canberra are struggling to understand whether Mr. Duterte’s tough talk is merely hot air or if he really intends to cut loose from their decades-old partnership.
In China, the picture appears equally murky.
His apparent antipathy to the U.S. is seen as a windfall for Beijing’s long-term effort to establish itself as the apex power in the region and weaken the defense partnerships through which Washington has dominated Asia militarily since 1945. Mr. Duterte’s remarks also bode well for Beijing’s attempts to undermine an international tribunal’s July ruling against its South China Sea maritime claims in a case brought by the previous Philippine administration.
Even so, Chinese authorities calculate that Mr. Duterte could change direction at any point and would lose popular support if he was seen to concede too much to Beijing on the South China Sea dispute.
“With Duterte’s temper, no matter who he’s blasting, it won’t be easy for him to be used by any third party,” the Global Times, a jingoistic tabloid affiliated with the Chinese Communist Party’s main newspaper, the People’s Daily, wrote. “In the long run, it may not be easy for China to deal with him either.”
Discerning his long-term strategy—if there is one—is made more difficult by confused communications from the 2½-month-old administration. His spokesmen routinely tell the media the president, who has a penchant for coarse language, didn’t really mean what he had just said.
Sen. Panfilo Lacson, an independent Philippine lawmaker, lashed out at the president’s press officers Wednesday, saying they were “damaging the credibility not only of the head of state but of the country.” Whatever the president says should be considered official policy, no matter how controversial, he said.
Mr. Duterte’s spokesmen didn’t respond to questions sent Wednesday.
In recent days, the 71-year-old Mr. Duterte has said the Philippines would stop patrolling the South China Sea alongside the U.S. Navy to avoid being part of any “hostile act” toward Beijing; called for the departure of some U.S. troops and said he would pursue a more independent foreign policy and shop for weapons in China and Russia.
The official response Wednesday in Beijing was vague.
“For China’s part, we are willing to work with the Philippines to promote and resume bilateral cooperation across the board,” a Foreign Ministry spokeswoman said. Asked about Mr. Duterte’s assertion that Beijing had offered favorable terms for arms purchases, she said she had no information.
It also would be costly for Manila: The U.S. alliance provides the Philippine military—one of the least-effective fighting forces in the region—with a more-credible deterrent against any aggression.
“This is a risky and dangerous strategy” that would alienate regional allies, prove unpopular with the overwhelmingly American-friendly public and appall the Philippine military, which has worked hand in glove with the U.S. military for decades, said Ian Storey, a senior fellow at the ISEAS Yusof Ishak Institute in Singapore.
“Duterte has brought to a grinding halt the forward momentum in Philippine-American relations,” said Mr. Storey.
In Mr. Duterte’s eyes the Philippines has been poorly served by the alliance. American meddling has stoked the Philippines’ long-running insurgencies, he has said. He also has faulted Washington for failing to check China’s island-building in the South China Sea, and for providing insufficient hardware to the ill-equipped Philippine military.
U.S. military and security assistance to the Philippines this year is budgeted at $120 million, equivalent to about 3% of Manila’s defense budget.
With a huge majority in Congress, Mr. Duterte faces little political opposition at home. But comments on social media about his turn away from the U.S. toward China seemed to be overwhelmingly negative.
“What he’s really saying is, ‘I surrender to China,’” one Facebook user wrote.
Former Philippine Ambassador to the U.S. Jose Cuisia, who stepped down in June, criticized the decision to end joint patrols and said Mr. Duterte was wrong to play down the value of the American alliance.
“When you look at what the U.S. provided us over the past six years, it’s been quite substantial and you have to appreciate that,” he said in a television interview Wednesday.
Philippine President Rodrigo Duterte further strained his country’s ties with the U.S., Manila’s most important military ally, by calling for the departure of American troops from troubled Mindanao island, where they serve as military advisers. Photo: Getty Images
U.S. State Department spokesman John Kirby said this week that Mr. Duterte’s incendiary remarks were “unhelpful,” and that the U.S. government was waiting to see whether his tough statements would translate into official policy.
Japan also risks a setback in its efforts, under Prime Minister Shinzo Abe, to build alliances with Southeast Asian nations and Australia as a counterweight to China.
Just last week, Mr. Abe met Mr. Duterte for the first time. Japan agreed to provide low-interest loans to allow the Philippines to buy two more large patrol vessels, on top of 10 smaller vessels already promised. Japan also said it would lease five TC-90 military training planes, which can be used for surveillance, and Mr. Abe told Mr. Duterte that Japan hopes to offer assistance in training pilots and mechanics.
The Japanese Foreign Ministry declined to comment on Mr. Duterte’s statements Wednesday. South Korea, which also sells arms to the Philippines, also declined to comment.
Professor Narushige Michishita at the National Graduate Institute for Policy Studies in Tokyo said the fear for the region is that a shift by Manila “could give China a chance to create splits” among countries around the South China Sea. “And the risk that China would become more assertive in the East China Sea would rise,” he added.
Gregory Poling of the Center for Strategic and International Studies, a U.S. think tank, said U.S. efforts to enforce the rule of law in the South China Sea, and reassert its leadership in the Asia-Pacific more generally, would be “undermined” by any Philippine retreat from the alliance.
While Mr. Duterte’s anti-American views aren’t new, his decision to air them now may have been sparked by international criticism regarding his continuing “war on drugs,” in which police say nearly 3,000 people have died June 30, when he took office.
Mr. Duterte used an expletive last week in warning the U.S. president not to lecture him on human rights. Mr. Obama canceled their planned meeting.
“If you want to attack me or to lecture me, do not do it in public, just like one president and the U.N.” did, Mr. Duterte said on Tuesday. “You know when you lecture me, I get mad.”
—Jeremy Page and Te-Ping Chen in Beijing and Chieko Tsuneoka in Tokyo contributed to this article.
Write to Trefor Moss at Trefor.Moss@wsj.com
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