The White House has cancelled a scheduled meeting Monday between President Obama and Philippines President Rodrigo Duterte, after the controversial leader warned Obama not to raise human-rights issues and called him a son of a whore.

National Security Council spokesman Ned Price gave no explanation for the cancellation of the bilateral meeting at a regional summit in Laos, saying only that Obama will instead meet with President Park of the Republic of Korea.

Speaking at the G20 summit in China on Monday morning, Obama said he had heard about Duterte’s “colorful” remarks and instructed his staff to see if meetings with Duterte would still be “productive.”

Duterte said before flying to Laos that he is a leader of a sovereign country and is answerable only to the Filipino people. He was answering a reporter’s question about how he intends to explain the extrajudicial killings to Obama. More than 2,000 suspected drug pushers and users have been killed since Duterte launched a war on drugs after taking office on June 30.

In his typical foul-mouthed style, Duterte responded: “I am a president of a sovereign state and we have long ceased to be a colony. I do not have any master except the Filipino people, nobody but nobody. You must be respectful. Do not just throw questions. Putang ina I will swear at you in that forum,” he said, using the Tagalog phrase for son of a b—-.

Duterte has earlier cursed the pope and U.N. Secretary-General Ban Ki-moon.

The cancelled meeting was supposed to take place on the sidelines of the summit of the Association of Southeast Asian Nations.

“Who is he to confront me?” Duterte said, adding that the Philippines had not received an apology for misdeeds committed during the U.S. colonization of the Philippines.

He pointed to the killing of Muslim Moros more than a century ago during a U.S. pacification campaign in the southern Philippines, blaming the wounds of the past as “the reason why (the south) continues to boil” with separatist insurgencies.

Duterte also pointed to human rights problems in the United States.

Last week, Duterte said he was ready to defend his bloody crackdown on illegal drugs, which has sparked concern from the U.S. and other countries.

Duterte said he would demand that Obama allow him to first explain the context of his crackdown before engaging the U.S. president in a discussion of the deaths.

The Associated Press contributed to this story.