Philippine President Rodrigo Duterte has called Barack Obama a "son of a wh*re" as he vowed not to be lectured by the US leader on human rights when they meet in Laos.
The acid-tongued Duterte bristled at warnings he would face questioning by the US president over his bloody crackdown on illegal drugs that has claimed more than 2400 lives in just over two months.
"You must be respectful. Do not just throw away questions and statements. Son of a whore, I will curse you in that forum," Duterte told a news conference shortly before flying to Laos to attend the summit. "We will be wallowing in the mud like pigs if you do that to me."
Duterte was due to hold a bilateral meeting with Obama this afternoon on the sidelines of a summit of global leaders hosted by the Association of Southeast Asian Nations (ASEAN) in Vientiane, the Lao capital.
Duterte was elected in May after a promise to wage an unprecedented war on illegal drugs that would see tens of thousands of suspects killed.
Official figures released on Sunday show that, since Duterte took office on June 30, over 2400 people have been killed in police anti-drug operations and by suspected vigilantes.
Duterte has angrily rejected criticism from the Catholic Church, human rights groups, legislators and the United Nations.
Duterte vowed yesterday the bloodbath would continue as he pursued his goal of eradicating illegal drugs in the Philippines.
"More people will be killed, plenty will be killed until the last pusher is out of the streets. Until the (last) drug manufacturer is killed, we will continue and I will continue," he said.
Duterte insisted he would not take orders from the United States, a former colonial ruler of the Philippines, and did not care about how he was perceived.
"I don't give a sh*t about anybody observing my behaviour," he said.
Duterte also used vulgar language to accuse his domestic critics of wanting to please the United States.
"There are others who have the mental capacity of dogs who lap at the ass of the Americans," he said in reference to his critics.
Obama says he has asked his staff to assess whether it would be productive for him to meet with Duterte.
Obama said he had heard about the comment and instructed his aides to determine whether it would still be "constructive" to hold the face-to-face meeting.
Duterte is notorious for using offensive language. During the election campaign Duterte described the US ambassador to Manila as a "son of a wh*re" and being homosexual.
This was in response to the ambassador's criticism of Duterte for making a joke about wanting to rape a "beautiful" Australian missionary who was killed in a Filipino jail.