US President Barack Obama has cancelled a meeting with controversial Philippine President Rodrigo Duterte, who had earlier called him a “son of a whore”.
Mr Obama had said he would raise the issue of drug-related extrajudicial killings in the Philippines.
But Mr Duterte, who has sanctioned the killing of drug dealers, said if that happened: “Putang ina (son of a whore) I will swear at you in that forum.”
Aides say Mr Obama will now meet South Korea’s president instead.
US National Security Council spokesman Ned Price told reporters the US president would hold talks with Park Geun-hye at the Association of Southeast Asian Nations (Asean) in Laos, where leaders are gathering for a regional summit.
Mr Obama, who flew to Laos after attending the G20 meeting in Hangzhou, China, had been set to raise concerns about human rights abuses in the Philippines.
But speaking in Manila on Monday before he left for Laos, Mr Duterte bristled at the suggestion, saying it was “rude” and cursing the US president. He added that: “We will be wallowing in the mud like pigs if you do that to me.”
He then referred to the anti-drugs campaign that has led to the killing of 2,400 suspected drug dealers and users in the Philippines since he took office in June.
“The campaign against drugs will continue. Many will die, plenty will be killed until the last pusher is out of the streets….until the [last] drug manufacturer is killed we will continue.”
Mr Obama initially appeared to play down the insult saying that he had asked his aides to work out if this is “a time where we can have some constructive, productive conversations”.
His aides later cancelled the talks.
Mr Obama’s last scheduled trip to Asia as president has not been without incident: he was also caught up in a protocol row with hosts China over his arrival in Hangzhou.
A history of insults
This is not the first time President Duterte has employed vitriolic language against such prominent figures.
He has called Pope Francis the “son of a whore”, Secretary of State John Kerry “crazy” and recently referred to the US ambassador to the Philippines a “gay son of a whore” .
Correspondents say that such colourful talk plays well with the domestic audience, but it could cost Mr Duterte on the international stage.
The UN has repeatedly condemned Mr Duterte’s policies as a violation of human rights. In August, two UN human rights experts said Mr Duterte’s directive for police and the public to kill suspected drug traffickers amounted to “incitement to violence and killing, a crime under international law”.
This round of Asean talks comes against the backdrop of tensions over China’s territorial ambitions in the South China Sea – the Philippines and the US are key players in that debate.