The Philippines yesterday officially informed the United States that it was terminating a pact allowing American troops to hold military exercises in the country.
Foreign Secretary Teodoro Locsin has already sent to the US Embassy in Manila a letter saying the Philippines is ending its Visiting Forces Agreement (VFA) with the US, a top Foreign Ministry official said on Twitter.
Signed in 1998, the VFA gave legal cover to thousands of US troops who were rotated in the Philippines for military exercises and humanitarian assistance operations.
Last month, President Rodrigo Duterte threatened to repeal the pact over a US decision to deny entry to his political ally Ronald dela Rosa.
Mr dela Rosa was a police chief who served as an enforcer of Mr Duterte's deadly anti-drugs crackdown in 2016.
Thousands of mostly poor suspects were killed under the campaign, alarming the US and other Western governments.
Mr Duterte has made no secret of his deep resentment over what he sees as US insults and arrogance.
He still seethes over an incident in 2002, when supposed US government agents spirited Michael Meiring, a self-styled American treasure hunter who accidentally set off an explosive in his hotel room, out of Davao city.
Mr Duterte was mayor of Davao at the time. He vowed never to go to the US after Washington denied him a visa and cancelled his partner's US work visa soon after the Meiring incident.
Mr Duterte's allies had tried to dissuade him from terminating the VFA, saying a review would be a more appropriate response.
Mr Locsin said abrogating the accord would undermine the Philippines' security and foster aggression in the disputed South China Sea.
It would mean scrapping more than 300 joint activities with US forces "which the Philippine military and law enforcement agencies need to enhance their capabilities in countering threats to national security", he said.
American forces have provided intelligence, training and aid that allowed the Philippines to deal with human trafficking, cyber attacks, illegal narcotics and terrorism.
The US military presence has also served as a deterrent to aggressive actions in the disputed South China Sea, said Mr Locsin.
Yesterday, Mr Duterte's spokesman told reporters: "It's about time we rely on ourselves. We will strengthen our own defences and not rely on any other country."
In a statement, the US Embassy in Manila said the VFA's termination "is a serious step with significant implications for the US-Philippine alliance". "We will carefully consider how best to move forward to advance our shared interests," it said.
US Assistant Secretary of State for Political-Military Affairs R. Clarke Cooper told reporters on Monday that all current military exercises between Philippine and US troops would now be "put at risk".
"All the engagements, all the freedom of navigation operations, all the exercises, all the joint training, having US military personnel in port, on the ground, on the flight line... require that we have a mechanism that allows that, and that's why the VFA is so important," he said.
He said a separate defence pact signed in 2014, the Enhanced Defence Cooperation Agreement, might also have to be reconsidered.
That agreement allowed the extended stay of US forces and authorised them to build and maintain barracks and warehouses and store defence equipment and weapons inside five designated Philippine military camps.
Senator Panfilo Lacson said the broader Mutual Defence Treaty, which required the US to come to the Philippines' aid in the event of an invasion, "will now be reduced to a mere paper treaty".