MANILA - A former top diplomat on Wednesday called for public action against President Rodrigo Duterte's decision to terminate the Philippines' Visiting Forces Agreement (VFA) with the United States, urging Congress and the Supreme Court to take the lead.

In a statement, Albert del Rosario, a former foreign affairs secretary and envoy to the United States, hit Malacañang's move to abrogate the treaty, saying the administration's shift in foreign policy was a "national tragedy. "

"What is unfolding before us must be considered a national tragedy which should be resisted. It is our earnest hope that this most unfortunate decision to abrogate can be revisited," he said.

"Our people must take a stand. We appeal to our esteemed institutions such as Congress and the Supreme Court to lead us."

Duterte ordered the termination of the VFA after the US canceled for still undisclosed reasons the visa of his long-time ally, Sen. Ronald Dela Rosa, among chief enforcers of his bloody drug war.

On Tuesday, Malacañang sent its notice of termination to the US, a move that the American embassy in Manila called a "serious step with significant implications" on the long-standing alliance.

For Del Rosario, the VFA cancellation effectively terminates the country's other defense treaties with the US.

"The termination of the VFA by President Duterte can be viewed as ultimately putting an end to the Enhanced Defense Cooperation Agreement (EDCA) and the Mutual Defense Treaty (MDT)," said Del Rosario, chair of think tank Stratbase ADR Institute.

The MDT is a 1951 defense agreement that obligates both sides to come to each other's defense in case on a attack.

The VFA, a 1998 treaty, governs the conduct of American troops in the Philippines, while the 2014 EDCA is an executive agreement that allows for greater rotational presence of US troops in the Philippines.

Del Rosario further hit the Duterte administration's pivot away from the US and towards non-traditional allies, stopping short of naming China in his statement.

"This continuing shift in foreign policy casting aside a long time reliable ally in favor of an aggressive neighbor that has been blatantly demonstrating its lack of respect for international law is incomprehensible and harmful to our country and our people," said Del Rosario, in apparent reference to China's continuing incursions in the Philippines' exclusive economic zone in the disputed South China Sea.

It was during Del Rosario's time as top diplomat that the Philippines initiated arbitration proceedings against China over the resource-rich South China Sea, which Beijing claims in near entirety.

The ruling, which invalidated China's excessive claims, came out early in the administration of Duterte, who has pursued closer ties with Beijing. China has ignored the ruling.

"We must be with responsible nations with whom we share our core values of democracy, respect for human rights and the rule of law. To stand otherwise, is not what Filipino are; it is not what we do; it is not what is right," Del Rosario said.