Syria's president has said that he feels no guilt about his crackdown on a 10-month uprising, despite reports of brutality by security forces. In an interview with the US network ABC, Bashar al-Assad said he had given no orders for violence to be used against protesters but admitted "mistakes" were made. He said he did not own the security forces or the country. At least 4,000 people have been killed since the uprising began, the UN says. However, Mr Assad said the UN was not credible. Syria blames the violence on "armed criminal gangs". The US later rejected President Assad's assertions that he did not order the killing of protesters. "It is just not credible," White House spokesman Jay Carney said. "The United States and many, many other nations around the world who have come together to condemn the atrocious violence in Syria perpetrated by the Assad regime know exactly what's happening and who is responsible." Mr Assad's interview comes a day after the US announced that its ambassador in Syria, Robert Ford, would return to Damascus after he was withdrawn in October because of security concerns. France's ambassador returned on Monday. 'Big difference' Responding to questions from veteran presenter Barbara Walters about the brutality of the crackdown, Mr Assad said he did not feel any guilt. "I did my best to protect the people, so I cannot feel guilty," he said. "You feel sorry for the lives that has [sic] been lost. But you don't feel guilty - when you don't kill people." "We don't kill our people… no government in the world kills its people, unless it's led by a crazy person," he added. The security forces were not his, nor did he command them, the Syrian president said. "There was no command, to kill or to be brutal," he said. "I don't own them, I am president, I don't own the country so they are not my forces." Instead he blamed the violence on criminals, religious extremists and terrorists sympathetic to al-Qaeda, who he said were mingling with peaceful protesters. He said most of those killed were from government supporters, with 1,100 soldiers and police among the dead. Those members of the security forces who had exceeded their powers had been punished, he said. "Every 'brute reaction' was by an individual, not by an institution, that's what you have to know," he said. "There is a difference between having a policy to crack down and between having some mistakes committed by some officials. There is a big difference." When challenged about reports of house-to-house arrests, including of children, Mr Assad said the sources could not be relied upon. "We have to be here to see. We don't see this. So we cannot depend on what you hear," he said. The United Nations, which has said the Syrian government committed crimes against humanity, was not credible, Mr Assad said. He described Syria's membership of the UN as "a game we play". Asked if he feared sharing the fate of the late Libyan leader Muammar Gaddafi or ousted Egyptian President Hosni Mubarak, Mr Assad said the only thing he was afraid of was losing the support of his own people.