US President Barack Obama has cancelled a planned meeting with Philippines leader Rodrigo Duterte, the White House said Monday, after his Asian ally launched a foul-mouthed tirade against him.
Duterte called Obama a "son of a whore" hours earlier, vowing he would not allow the American leader to lecture him on human rights.
"President Obama will not be holding a bilateral meeting with President Duterte of the Philippines this afternoon," National Security Council spokesman Ned Price said.
"Instead, he will meet with President Park (Geun-hye) of the Republic of Korea."
Obama had been set for a showdown with firebrand Duterte on Tuesday as a regional summit gets underway in Asia, and amid tensions over China's growing territorial ambitions.
The pair were scheduled to meet in Laos at a gathering organised by the Association of Southeast Asian Nations, an annual event meant to foster harmony that often instead highlights regional rows.
However, shortly before flying to the capital Vientiane, Duterte launched a tirade at Obama.
"Son of a whore, I will curse you in that forum," Duterte told reporters when asked about Obama's plans to raise concerns over a war on crime in the Philippines that has seen more than 2,400 people killed.
The focus was meant to be on the surprising spat between the two longtime allies that have seen relations plunge under a barrage of foul-mouthed insults from Duterte since he came to office on June 30.
Duterte has previously also branded the US ambassador to Manila a "son of a whore" -- a term the acid-tongued former prosecutor commonly uses -- and criticised the US over its own track record of police killings.
- Crucial time –
The setback in relations between the United States and the Philippines comes at a crucial time in the region, with China seeking to cement control over the contested South China Sea.
The Philippines, Vietnam, Malaysia, Brunei and Taiwan also have competing claims to the strategically vital waters, but have watched China expand its presence by building artificial islands in key locations.
An international tribunal ruled in July that Beijing's claims to the waters -- through which $5 trillion in global shipping trade passes -- had no legal basis.
The ruling was widely seen as a sweeping victory for the Philippines, which filed the suit under the previous administration of Benigno Aquino.
But China has vowed to ignore the tribunal's decision.
Obama's aides had previously said he wanted to discuss the South China Sea issue with Duterte.
Under Aquino, the Philippines had forged closer military ties with the United States to deal with the China threat. But Duterte has cast doubt on that strategy.
He has also sought to heal relations with China rather than inflame them by pressing the tribunal's ruling.
Nevertheless, the South China Sea issue is expected to once again be discussed at the three days of meetings hosted by ASEAN.
The gathering will see the 10 members of ASEAN meet among themselves, then with leaders from China, Japan, South Korea and the US.
Other leaders to come for an East Asia summit on Thursday include from Australia, India and New Zealand.
Obama's time in Laos will be the final trip to Asia of his eight-year presidency, during which he has sought to refocus American military, political and economic resources on the region.
In one of the last acts of his so-called "pivot" to Asia, Obama is expected to announce greater help in clearing bombs dropped by US forces on Laos during the Vietnam War.
Obama will then travel to the ancient capital of LuangPrabang on Wednesday, visiting a historic temple and meeting with students at a university growing up in a tightly controlled communist nation.