Watch the Philippine president call Obama a 'son of a b****'

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We wouldn't exactly term this delicate diplomacy: in a recent speech the new Philippine president Rodrigo Duterte called Barack Obama a "son of a b****".

In the speech, he also warned Obama not to challenge him over extra-judicial killings in the Philippines, ahead of a regional summit in Laos.

This caused Obama to call off their planned meeting today. "Clearly, he's a colourful guy," he said. "What I've instructed my team to do is talk to their Philippine counterparts to find out is this in fact a time where we can have some constructive, productive conversations."

Rodrigo Duterte.
(Bullit Marquez/AP)

Duterte has been under intense global scrutiny over the more than 2,000 suspected drug dealers and users killed since he took office in May. Obama had said he planned to raise the issue in his first meeting with Duterte, but the Philippine leader insisted he was only listening to his own country's people.

"You must be respectful," Duterte said of Obama. "Do not just throw questions."

Using the Tagalog phrase for "son of a b****", he said: "Putang ina I will swear at you in that forum."

Barack Obama.
(Carolyn Kaster/AP)

Obama showed that he would not be intimidated by Duterte, saying he would "undoubtedly" still bring up human rights and due process concerns "if and when" the two do meet.

Duterte has since expressed regret over his offensive remark. In a statement read out by his spokesman, Duterte said his "strong comments" to certain questions by a reporter "elicited concern and distress, we also regret it came across as a personal attack on the US president".

This is not the first time that Duterte has received criticism for his language, having cursed both the Pope and UN Secretary Ban Ki-Moon in the past.