US President Barack Obama has cancelled a planned meeting with Rodrigo Duterte after the Philippines leader labelled him a "son of a whore" in a foul-mouthed tirade.
The pair had been due to hold a bilateral meeting on the sidelines of a gathering of global leaders in the Laos capital Vientiane.
Mr Duterte had bristled at warnings he would face questioning by Mr Obama over a war against drugs in the Philippines that has claimed more than 2,400 lives in just over two months.
Police say about 900 of those killed died in police operations, and the rest were "deaths under investigation", a term human rights activists say is a euphemism for vigilante and extrajudicial killings.
Mr Duterte made it clear he would not be lectured on human rights by Mr Obama, saying: "Who is he to confront me?"
"You must be respectful. Do not just throw away questions and statements. Son of a whore, I will curse you in that forum," Mr Duterte told a news conference shortly before flying to Laos.
"We will be wallowing in the mud like pigs if you do that to me."
Mr Obama cancelled the talks in response to the comments, the White House said, adding the President will instead meet with South Korean President Park Geun-hye.
The move came hours after the US President cast doubt on the planned talks, saying he had asked his team to find out if "constructive, productive conversations" were possible.
"Obviously the Filipino people are some of our closest friends and allies and the Philippines is a treaty ally of ours," he told reporters at a G20 meeting in China before he travelled to Laos.
"But I always want to make sure that if I'm having a meeting that it's actually productive and we're getting something done.
"What is certainly true is that the issues of how we approach fighting crime and drug trafficking is a serious one for all of us, and we've got to do it the right way."
South Korea's response to North Korea's latest missile tests is expected to be on the agenda for the meeting between Mr Obama and Ms Park when they meet on the sidelines of the Association of Southeast Asian Nations (ASEAN) summit.
It is not the first time Mr Duterte has cursed at a world leader. He called Pope Francis a "son of a whore" in May, and called US Ambassador Philip Goldberg a "gay son of a whore".
The former crime-busting mayor of southern Davao city won the presidency in May promising to suppress crime and wipe out drugs and drug dealers.
While his campaign has won popular support, the killings have alarmed rights groups and brought expressions of concern from the United States, a former colonial power and a close Philippine ally, and the United Nations.
Reuters