Philippine President Rodrigo Duterte arrives at the ASEAN Summit family photo while U.S. President Barack Obama chats with the Sultan of Brunei Hassanal Bolkiah in Vientiane, Laos September 7, 2016. REUTERS/Jorge Silva

By Manuel Mogato

VIENTIANE (Reuters) - U.S. President Barack Obama and Philippine President Rodrigo Duterte shook hands and had a brief chat on Wednesday, officials said, easing a standoff after Duterte called Obama a "son of a bitch" ahead of a summit of Asian leaders in Laos.

The presidents of the two longtime allies were due to hold talks on Tuesday but the White House canceled the meeting after Duterte's insult.

"I'm very happy that it happened," Philippines' foreign minister, Perfecto Yasay, said of their short meeting.

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

Duterte had his outburst on Monday when he was defending his war on drugs that has killed at least 2,400 Filipinos.

Notorious for his tirades and for cursing during interviews and speeches, he later expressed regret for offending Obama.

The two men shook hands and chatted for about two minutes as they waited to take their seats at a gala dinner ahead of Thursday's East Asia Summit, according to Yasay and several of Duterte's aides.

Alan Cayetano, who was Duterte's vice-presidential running mate in this year's election, described the atmosphere as "warm and cordial", while a White House official said "the exchange consisted of pleasantries between the two".

Tensions between the United States and the Philippines, its former colony, are unusual at high-level meetings.

The two countries are treaty allies and Washington has strongly backed Manila's calls for China to abide by a recent ruling over the South China Sea, which the Philippines won.

China is among the countries taking part in Thursday's summit, which includes the 10 Association of South East Asian Nations member states and Japan, South Korea, Australia, India, Russia and the United States

Philippines ambassador to Laos, Marciano Paynor, said the tiff with Obama was part of a learning curve for Duterte, who needed a chance to make the transition from being a city mayor to a head of state.

"He has to experience it," he said. "If you don't experience it, you don't know how it's done, you'll be grappling."

(Additional reporting by Roberta Rampton; Writing by Martin Petty; Editing by Louise Ireland)