China is "threatening war" after it authorised its warships to open fire on fishers plying traditional waters, warns the Philippines. Now Washington says it has Manila's back.
Beijing has passed legislation calling upon its military-controlled coast guard to open fire upon "foreign" vessels and destroy "illegal" structures within the East and South China seas.
Problem is, those territories don't belong to it.
Which means the law represents a significant escalation in international tensions.
And that has Manila worried the region is about to erupt in violence.
Foreign Secretary Teodoro Locsin Jr. says the Chinese move "is a verbal threat of war to any country that defies the law". Any nation not rejecting the law will be signalling its "submission".
Beijing's aggressive new legislation orders its coast guard to "take all necessary measures, including the use of weapons, when national sovereignty, sovereign rights, and jurisdiction are being illegally infringed upon by foreign organisations or individuals at sea".
Hours after the new law was passed, a flight of H-6K strategic bombers escorted by advanced fighters made a dummy "attack run" on the USS Theodore Roosevelt battle group.
Filipino fishers operating out of Thitu (also known as Pag-asa) island in the Spratly Islands also reported Chinese coast guard and militia vessels forcing them out of traditional waters.
Making a stand
New US Secretary of State Antony Blinken has responded to Beijing's intimidation by contacting Mr Locsin, telling him the longstanding defence agreement between the two nations would be honoured.
"Secretary Blinken pledged to stand with Southeast Asian claimants in the face of PRC pressure," a State Department press release reads. "Secretary Blinken stressed the importance of the Mutual Defence Treaty for the security of both nations, and its clear application to armed attacks against the Philippine armed forces, public vessels, or aircraft in the Pacific, which includes the South China Sea."
The new Chinese law dramatically raises the stakes of an armed clash in the region.
And posturing such as the two dummy air attacks on the US aircraft carrier battlegroup increases the odds of an incident.
Neither side is showing signs of backing down.
Earlier this month, the US military warned it planned to be "more assertive" against international law violations in the Pacific Ocean and the East and South China seas.
"Our globally deployed naval forces interact with Chinese and Russian warships and aircraft daily," the statement reads. It highlighted the "growing aggressiveness" of encounters and declared China "the most pressing, long-term strategic threat".
The East China Sea is bracketed by Taiwan, North and South Korea, Japan and China.
The South China Sea is bracketed by Taiwan, the Philippines, Vietnam, Malaysia, Brunei, Indonesia and China.
After World War II, China signed the international law of the sea which allocates specific portions to each nation under clearly defined criteria.
Beijing insists these don't apply to it.
It says both seas belong to it based on historical ownership.
A 2016 ruling by the international court of arbitration judged this assertion to be without merit.
Now, US President Joe Biden has "underscored that the United States rejects China's maritime claims in the South China Sea to the extent they exceed the maritime zones that China is permitted to claim under international law".
On Monday, Mr Duterte's office issued a statement saying he hoped no country would do anything to increase tensions further. His foreign minister later expressed concerns the Philippines was about to lose access to its western exclusive economic zone (EEZ).
The law "is virtually a declaration of war against countries that are legitimate claimants of the Chinese-claimed marine territory," fishing federation chairman Fernando Hicap told the Hong Kong based South China Morning Post.
Concern has been growing at the militarisation of China's civilian coast guard and fishing fleets.
The Coast Guard has recently been put under the operational control of the People's Liberation Army Navy. Analysts saw this as a disturbing move as coast guards are supposed to be a civilian policing force.
Beijing has long sent its political commissars to sea with its enormous fishing fleets. But, in recent decades, these fleets have also undergone cooperative naval training.
"The white ships of the coastguard symbolise maximum tolerance at all times to protect civilians and merchants at sea," Philippines defence analyst Chester Cabalza says. Grey warships are "symbols of antagonism and war".
"(Now) Chinese coastguard can just shoot anyone, armed or unarmed, in territorial waters that they illegally claim. This is a serious threat to Filipino fishers … in our very own territorial waters."
Meanwhile, resentment among the Filipino community is rising.
One fisher told local TV he had been barred from sandbars surrounding Thitu Island by Chinese coast guard and militia.
"Of course I'm furious, we used to be able to go there, that's ours," he said. "Why would they forbid us to go there now?"
Another fisher released a short video account: "I have many enemies at sea. Look. Those are Chinese ships in front of me. They're blocking me and I can't get to sandbar two," Larry Hugo states. "I will leave first."
'Not good for peace'
Beijing has again warned that the US's ongoing military presence in the South China Sea is "not conducive to peace". China's foreign ministry stated earlier this week that US freedom-of-navigation operations designed to "flex its muscles" were threatening the region's stability.
Meanwhile, the USS Theodore Roosevelt aircraft carrier battle group passed China's illegal artificial island fortresses in the Spratly Islands.
Satellite imagery reveals ships in the group passed close to Beijing's 12 nautical mile territorial boundary claim.
But China continues to ramp up its efforts to enforce its territorial ambitions arbitrarily.
Publication Defence News reports an analysis of satellite imagery has revealed a recent build-up of Chinese surveillance aircraft on Hainan Island at the northern extremity of the South China Sea.
Work is well underway on enormous dry docks big enough to support China's future force of aircraft carriers. And Woody Island in the Paracels has been undergoing further land reclamation efforts to protect its military airfield facilities from erosion.
• Jamie Seidel is a freelance writer | @JamieSeidel