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 Duterte was responding to the US president's promise to raise the issue of drug-related extra-judicial killings in the Philippines at their meeting.

The Philippine leader, known for his colourful language, has insulted prominent figures before, but this time it has had diplomatic consequences.

He has now said he regrets the remark.

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

Both presidents are among leaders gathering for the Association of Southeast Asian Nations (Asean) summit in Laos.