President Rodrigo Duterte has ordered the termination of the two-decade-old Visiting Forces Agreement with the United States, his spokesman said on Friday.

Presidential Spokesperson Salvador Panelo told reporters that Foreign Affairs Secretary Teodoro Locsin Jr. has told the members of the VFA Commission, particularly Defense Secretary Delfin Lorenzana, who is vice-chair, to begin the process of ending the treaty. Locsin is the chairman of the commission.

"So according to Secretary Locsin, he's supposed to be departing anytime, a few hours from now to the US but he said he has already called the committee to start the process...of terminating," he said.

Locsin tweeted that he would go to the US on "a totally unrelated matter."

The Department of Foreign Affairs chief said that he started the process of terminating the VFA by contacting the Senate because "it is a treaty on our side, an executive agreement on the US side."

Under the Philippine Constitution, in order for a treaty to be effective, it has to be concurred by at least two-thirds of all the members of the Senate.

Duterte's decision came after the US canceled the visa of Senator Ronald dela Rosa, his former chief of the Philippine National Police and responsible for his war on drugs since he assumed office in June 2016 until the latter's retirement in 2018.

Dela Rosa confirmed earlier this week that the US canceled his visa. He was not sure if the cancelation was in relation to a US law banning Filipino government officials responsible for the continued detention of opposition Senator Leila de Lima.

In a speech in Leyte Thursday night, Duterte only threatened to terminate the VFA if US would not "correct" itself in canceling Dela Rosa's visa. He said he was giving Manila and Washington one month to discuss the matter.

But according to Panelo, Duterte made his decision to end the VFA also Thursday night.

"I asked him (Duterte) last night when will the process start. (He said) tonight," he said.

The Philippines and the US signed the VFA on February 10, 1998. The treaty allows the elements of the armed forces of the US to visit the Philippines from time to time.

Panelo said the termination of the VFA would take effect 180 days from the date on which either party gives the other party notice in writing that it desires to terminate the agreement. Celerina Monte/DMS