Philippine President Rodrigo Duterte has threatened to end a pact key to annual war games with American troops if the U.S. does not restore the travel visa of an official who oversaw his drug war. This marks the latest in a long line of Duterte's threats to shrink or sever ties with historical ally Washington, which have periodically followed criticism of his deadly narcotics crackdown.

Duterte spoke after Ronald Dela Rosa – the former national police chief who is now a senator – who said the U.S. had canceled his visa but did not tell him why. Dela Rosa was the first enforcer of Duterte's internationally condemned campaign, in which police say they have killed just over 5,500 alleged dealers and users. Human rights advocates say the true toll is four times higher and could amount to crimes against humanity.

Duterte spoke on the attack in a speech late Thursday. "Now, they won't let Bato go to America," he said, using Dela Rosa's nickname. "If you do not make a correction there, one, I will terminate the bases – Visiting Forces Agreement," Duterte added. "I'm giving ... the American government one month from now."

The Visiting Forces Agreement (VFA) outlines the rules governing the conduct of U.S. troops participating in joint military exercises in the Philippines. The pact gave legal cover for the resumption of large-scale war games between the two allies after the U.S. military closed its Philippine bases in the 1990s amid rising anti-U.S. sentiment. Duterte also threatened in 2016 to cancel the agreement but has generally attacked ties with the U.S., including an announced "separation" from its former colonial master. Until now the president has not made good on those threats, some of which came after then-U.S. President Barack Obama was critical of Duterte's crackdown in 2016.

Relations between Washington and Manila under President Donald Trump, who has voiced support for Duterte, are on a stronger footing. However, recent criticism from U.S. lawmakers has introduced new tensions.

The Philippines in December barred U.S. senators Richard Durbin and Patrick Leahy, who were behind a measure to prevent officials involved in the incarceration of Senator Leila de Lima from entering the U.S. De Lima, one of the highest-profile critics of Duterte's narcotics crackdown, has been held since February 2017 over a drug charge that she claims was fabricated to silence her.