Call it Bongbong diplomacy. The Biden administration has a message for Communist China: America backs the Philippines. The message concerns a maritime dispute between that nation and China in the South China Sea.

A State Department statement siding with Manila represents a break with the  appeasement policies of the Obama era and indicates that Washington no longer sees Beijing as a potential partner. The question is whether this will be enough.

America “supports the Philippines in calling on [China] to end its provocative actions and to respect international law in the South China Sea,” the department’s spokesman, Ned Price, said in a written statement this morning.

America, Mr. Price added, shares Manila’s concerns about Beijing’s “provocative actions” near Second Thomas Shoal and Whitsun Reef, which are “within the Philippine exclusive economic zone.”

Beyond Beijing’s immediate action, Mr. Price wrote, China’s latest incursions into the Phillipines’s waters represents a “broader trend” of its “provocations against South China Sea claimants and other states lawfully operating in the region.” 

Although Mr. Price dutifully used language about the “rules-based international order,” his statement was worded to convey a clear message: In this dispute, America is siding squarely with the Philippines and will not entertain Communist China’s dubious sovereignty claims. 

Skeptics in Asia could be forgiven for noting that a State Department statement and a yuan or two will buy you a cup of tea in Beijing. Yet, Washington seems to favor a more assertive policy now than it did during President Obama’s tenure.

This is true even as Mr. Biden’s national security team is almost exclusively composed of that era’s personnel. Mr. Price, for one, was a spokesman for Mr. Obama’s National Security Council.

When a similar dispute in the last decade was brewing between Manila and Beijing, the White House seemed more concerned about harm to America’s growing bilateral trade with Red China than about siding with an ally. America decided to stay above the fray. 

At the time, the Obama administration declared that it would not interfere in a territorial dispute over the Philippines’ Spratly islands and the Scarborough Shoals in the South China Sea. Instead, Washington urged Manila and Beijing to resolve their differences judicially, at the International Court of Justice.

They did that, and in July 2016 the Hague court unanimously ruled  in favor of Manila. It determined that Beijing’s claims of sovereignty over the disputed areas, and its efforts to enforce them, were unlawful in international law.

Beijing quickly dismissed the ICJ ruling, arguing the global court had no jurisdiction to begin with. Disregarding the court, Communist China went on to erect military bases in various spots around the South China Sea, which it considers its own private lake. 

Shortly after Washington put the interests of a long-term Asian ally in the hands of an international court unrecognized by Beijing, a new president was elected in Manila.

That leader, President Duterte, turned his back on America, tightened relations with Beijing, and ridiculed the Hague ruling as “just paper.” Early in his presidency, Mr. Duterte announced the Philippines would shun America economically and militarily, and favor ties with China. 

With a new chief in place at Manila — President Ferdinand Marcos, Jr., known as Bongbong — Washington is attempting to win back an ally that since 1951 has shared a mutual defense treaty with America.

It will not be easy. Like his predecessor, Mr. Marcos has cultivated the Philippines’ relationship with Beijing and advocated a soft, diplomatic approach toward the Xi regime. In March, though, the Philippines and America conducted the largest joint military exercise in seven years.

America’s deputy secretary of state, Wendy Sherman, during her latest trip to Asia, stopped at Manila, where she met with Mr. Marcos in an attempt to reassure the new president that America is on his side. 

The new dispute, over what Manila’s foreign ministry calls Chinese “illegal fishing” in its territorial waters, may well reignite the war over the South China Sea. “China has no right to fish, monitor, or interfere with the Philippines’ legitimate activities therein,” Manila said in a statement. 

To impress Beijing, however, more than such statements are needed. After ignoring the international court’s ruling in the last decade, China went on to build artificial islands in the areas its “fishermen” have taken over from the Philippines, and erected military installations there.

Beijing employed similar tactics in waters near Taiwan, Vietnam, Indonesia, Brunei, and Malaysia, to name a few — and as far away as Japan’s Senkaku islands in the East China Sea. President Xi increasingly employs aggressive tactics to assert Beijing’s authority over waters in China’s near abroad and beyond — deep into the Pacific Ocean. 

Mr. Marcos, for now, is relying on diplomacy to stop Beijing’s new incursions into waters in the Philippines’ exclusive economic zone. Washington’s signal that this time America would back its ally is a first step.

It looks, though, like Mr. Biden will have to make clear to Beijing that to defend our allies in the Pacific, he is willing to go beyond diplomacy and that he would rely on more than legal determinations in global bodies that Beijing simply ignores.