Barack Obama met briefly with Philippine leader Rodrigo Duterte on Wednesday, their two governments said, days after the firebrand politician warned of throwing expletives at the US president.

The encounter took place just before a dinner during a summit of regional leaders in Laos, officials indicated.

"They met at the holding room and they were the last people to leave the holding room. I can't say how long they met," Foreign Secretary Perfecto Yasay, travelling with Duterte, told reporters shortly afterwards.

"I'm very happy that it happened."

In a terse statement, the White House said only that "Obama had a brief discussion with President Duterte before the ASEAN Gala Dinner in the leaders' hold space."

"The exchange consisted of pleasantries between the two."

Obama cancelled Tuesday's planned meeting with Duterte on the sidelines of the Association of Southeast Asian Nations-hosted summit after the acid-tongued Philippine president launched a barrage of insults the previous day.

His outburst was prompted by US assertions that Obama planned to raise the issue of Duterte's war on crime that has claimed 3,000 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 reporters when asked about his message for Obama.

"We will be wallowing in the mud like pigs if you do that to me."

Obama initially responded by calling Duterte a "colorful guy," but then called off the meeting after the international media reported heavily on the issue.

The snub was a spectacular setback for relations between the United States and Philippines, which are longtime allies and are bound by a mutual defense treaty to help each other in times of war.

The two countries also appeared to clash over the meaning of satellite imagery showing Chinese activity on a disputed reef off the coast of the Philippines.

Releasing the images Duterte's government said they had evidence China was taking steps to begin dredging -- a major escalation.

The White House tried to play down the claim, saying it believed Chinese activity in the area was at the same level as previous months.

Yasay sought to characterize Wednesday's meeting as proof the alliance was strong enough to withstand such hiccups.

"It all springs from the fact that the relationship between the Philippines and the United States is firm, very strong," Yasay said.

Nevertheless, Duterte's office earlier Wednesday released a statement saying he would sit next to Obama at the gala dinner.

"The media from all over the world, including from the Philippines, are up in excitement as each await the event where the two leaders will possibly say something positive," the statement from the presidential palace said.

However Obama did not sit next to Duterte.

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