The Philippines scrambled to defuse a row with the United States on Tuesday and its new president, Rodrigo Duterte, voiced regret for insulting President Barack Obama with the use of an expletive that prompted Washington to call off a bilateral meeting. The tiff between the two allies overshadowed the opening of a summit of East and Southeast Asian nations in Laos. It also soured Obama's last swing as president through a region he has tried to make a focus of US foreign policy, a strategy widely seen as a response to China's economic and military muscle-flexing. However, diplomats say strains with longtime ally the Philippines could compound Washington's difficulties in forging a united front with Southeast Asian partners on the geostrategic jostle with Beijing over the South China Sea. Duterte has bristled repeatedly at criticism over his "war on drugs," which has killed about 2,400 people since he took office two months ago, and on Monday said it would be "rude" for Obama to raise the question of human rights when they met. Such a conversation, Duterte told reporters, would prompt him to curse at Obama, using a Filipino phrase of a swear word." After Washington called off Tuesday's bilateral meeting between Obama and Duterte in response, the Philippines issued two statements expressing regret. "President Duterte explained that the press reports that President Obama would ‘lecture' him on extrajudicial killings led to his strong comments, which in turn elicited concern," the Philippines government said in one statement. "He regrets that his remarks to the press have caused much controversy," it added. "He expressed his deep regard and affinity for President Obama and for the enduring partnership between our nations." The White House had earlier said Obama would not pull any punches on his concerns about human rights abuses in the Philippines, its treaty ally, when meeting Duterte. Instead of the Duterte meeting, Obama plans to hold talks with South Korean President Park Geun-hye, said Ned Price, spokesman for the White House National Security Council - a meeting where the response to North Korea's latest missile tests is expected to be on the agenda. A Philippines official who declined to be named said there would be no formal meeting rescheduled in Laos but a short ‘pull-aside' conversation between the two presidents was still possible. Duterte vows to eat militants Philippine President Rodrigo Duterte has vowed to personally tear apart and eat Abu Sayyaf militants, in a bloodthirsty vow of revenge for deadly attacks. "They will pay. When the time comes, I will eat you in front of people," Duterte told an audience of Filipinos late on Monday night while in Laos for a regional summit. "If you make me mad, in all honesty, I will eat you alive, raw." Duterte often hurls abusive insults at critics and is waging a brutal war on crime in which nearly 3,000 people have been killed since he took office on June 30. His aides often urge reporters against taking Duterte's comments literally, cautioning that the 71-year-old former lawyer speaks in a crude language of the people. During the election campaign earlier this year Duterte attracted widespread criticism for saying he had wanted to rape a "beautiful" Australian missionary who had been sexually assaulted and murdered in a Philippine prison riot. Duterte, 71, also claimed to keep two mistresses in cheap boarding houses who he took to short-stay hotels for sexual encounters. Duterte on Monday offered a particularly vivid description of how he would like to eat Abu Sayyaf militants, who killed 15 soldiers last month and are accused of a bombing in his home city last week that claimed 14 lives. "I will really carve your torso open. Give me vinegar and salt and I will eat you. I'm not kidding," Duterte said, according to an official video of his speech posted on Tuesday. "These guys are beyond redemption." The Abu Sayyaf are a small band of militants based on remote southern islands of the mainly Catholic Philippines and are listed by the United States as a terrorist organisation. They are notorious for kidnapping foreigners to extract ransoms, and this year beheaded two Canadian hostages.