The United States stands by its assertion that the North Korean government was behind the massive cyberattack on Sony Pictures, a spokesman for the White House National Security Council said on Saturday.Asked about North Korea's statement on Saturday denying involvement in the strike against the Hollywood studio, NSC spokesman Mark Stroh said: "As the FBI made clear, we are confident the North Korean government is responsible for this destructive attack. We stand by this conclusion.""The Government of North Korea has a long history of denying responsibility for destructive and provocative actions," he said."If the North Korean government wants to help, they can admit their culpability and compensate Sony for the damages this attack caused," Stroh added. North Korea called earlier for a joint US-North Korean probe into the incident.