President Rodrigo Duterte has said his threat to pull the Philippines out of the United Nations for criticizing his deadly crime war was just a "joke", while attempting a light-hearted wordplay on genocide. Duterte on Sunday said he may withdraw the Philippines from the world body after a UN human rights expert said last week his encouragement of security forces to kill drug suspects violated international law. "Can't you take a joke," Duterte told reporters on Tuesday when asked if he was serious. Nearly 2,000 people have been killed since Duterte was sworn into office on June 30 and immediately launched his war on crime, according to the national police chief. Duterte has insisted most of the 756 people confirmed killed by police were drug suspects who resisted arrest, while the others died due to gang members waging warfare against each other. However rights groups, some lawmakers and others have said security forces are engaging in unprecedented extrajudicial killings. The US State Department also this week said it was "deeply concerned" about reports of extrajudicial killings. Duterte on Tuesday criticized Agnes Callamard, the UN special rapporteur on summary executions who said he was violating international law, branding her "ambitious" and "brainless". Duterte also said Callamard had accused him of genocide, which she did not. "That's the invention of a woman who wants to commit suicide," Duterte said, before offering his wordplay. "You can think of genocide, suicide or what, side by side, upper side, whatever, what if upper side or even upside?" A local reporter then joined in, offering "sunny side". Duterte smiled and said: "You reporters say that and then we will be the ones accused of saying that. You added something there." Duterte and his aides have previously cautioned reporters not to take everything the president says at face value. Duterte once promised 100,000 people would die in his war on crime with so many bodies dumped in Manila Bay that fish would grow fat from feeding on them. He also told a reporter he had personally killed three people. During the election campaign, Duterte attracted criticism for saying he wanted to rape a "beautiful" Australian missionary who was sexually assaulted and murdered in a Philippine prison. He later said it was not a joke, and refused to apologize. However, when pressed on the issue this month in an interview with Al Jazeera, presidential spokesman Ernesto Abella said the rape comment was a joke. Abella sought to explain that Duterte's humor and abusive comments were because he was Cebuano, referring to people from the central and southern Philippines. "The Cebuano subculture speaks in a very rough kind of humor," Abella said.