MANILA - Philippine President Rodrigo Duterte has expressed regret for his expletive-laced tirade against United States President Barack Obama, and said he looks forward to "ironing out our differences arising out of national priorities and perceptions".

"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," Mr Duterte said in a statement his office issued on Tuesday (Sept 6).

On Monday, Mr Duterte cautioned Mr Obama against questioning the more than 2,000 extrajudicial killings that have blighted his anti-crime push at an ongoing Asean summit in Vientaine, Laos.

Using a Tagalog phrase for "son of a w****", he warned Mr Obama: "Do not do it... We'll both just end up rolling in the mud... You must be respectful."

With those remarks, National Security Council spokesman Ned Price said later Mr Obama's meeting with Mr Duterte, set for Tuesday afternoon, was off.

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"President Obama will not be holding a bilateral meeting with President Duterte of the Philippines this afternoon," said Mr Price.

Mr Obama learned about the insult as he emerged from the Group of 20 summit in Hangzhou, China.

At a news conference, he said he had told his aides to speak with Philippine officials “to find out is this, in fact, a time where we can have some constructive, productive conversations”, signalling clearly that the meeting would not proceed as planned.

“I always want to make sure that if I’m having a meeting, that it’s actually productive and we’re getting something done,” Mr Obama told reporters.

In his statement, Mr Duterte said: "The meeting between the United States and the Philippines has been mutually agreed upon to be moved to a later date.

"Our primary intention is to chart an independent foreign policy while promoting closer ties with all nations, especially the US with which we have had a long-standing relationship," he said.

He added: "We look forward to ironing out differences arising out of national priorities and perceptions, and working in mutually responsible ways for both countries.”