VIENTIANE: United States (US) President Barack Obama on Tuesday pulled out of a bilateral meeting with Philippine President Rodrigo Duterte after the firebrand leader launched a tirade against him, calling him a son of a `*****`, during a press conference on Monday.

The acid-tongued former prosecutor on Monday warned he would not be lectured by Obama over concerns about extrajudicial killings and a brutal war against crime that has claimed more than 2,400 lives in the Philippines.

“You must be respectful. Do not just throw away questions and statements. Son of a `*****`, I will curse you in that forum,” Duterte told reporters when asked about his message for Obama.

The US and Philippine leaders were due to meet later Tuesday in the Lao capital of Vientiane at a gathering organised by the Association of Southeast Asian Nations.

Duterte 'regrets' attack

But later on Tuesday, Duterte expressed regret after his tirade against Obama.

“While the immediate cause was my strong comments to certain press questions that elicited concern and distress we also regret it came across as a personal attack on the US president,” a statement released by Duterte said.

Duterte's statement in Laos struck a much more conciliatory tone, claiming both sides would hold face-to-face talks “at a later date”.

“Our primary intention to chart an independent foreign policy while promoting closer ties with all nations especially the US with which we have a long standing partnership,” the statement said.

“We look forward to ironing out differences arising out of national priority perceptions and working in mutually responsible ways for both countries,” it added.

This is not the first time the Philippine president has used colourful language against politicians, diplomats and world leaders.

He earlier used a Tagalog language homophobic slur to express his displeasure with US Ambassador Philip Goldberg. "I'm fighting with (US Secretary of State John Kerry's) ambassador. His gay ambassador, the son of a `*****`. He `******` me off," Duterte said.

The controversial president has also disparaged the pope and others who controvert his worldview.

Memorable broadsides on Duterte's growing list of them

On the United Nations: “Maybe we'll just have to decide to separate from the United Nations. If you're that rude, son of a `*****`, we'll just leave you. So take us out of your organisation, you have done nothing here anyway.”

He made the remark at a news conference in August regarding remarks by UN-appointed rapporteurs about drug-related killings.

On a slain missionary: “I looked at her face, son of a `*****`, she looks like a beautiful actress in America. Son of a `*****`, what a waste.

The Philippine president made the remarks while joking at a campaign event in April about the gang rape and killing of an Australian missionary by inmates in a 1989 jail siege in the Philippine city of Davao while Duterte was mayor there.

On the Pope's visit: “I wanted to call him, 'Pope, you son of a `*****`, go home. Don't visit here anymore.”

The remark was made after a monstrous traffic jam that trapped Duterte and many others in January 2015. Duterte apologised after bishops condemned his language.