HONOLULU (AP) — Opening a new front in its cyber spat with North Korea, the United States slapped new sanctions Friday on government officials and the North’s defense industry in its first public act of retribution for a cyberattack against Sony. Despite lingering doubts by the cyber community, the U.S. insisted North Korea was to blame.The White House warned this is just the opening salvo in the U.S. response.While the fresh sanctions will have limited effect - North Korea already is under tough U.S. sanctions over its nuclear program - American officials portrayed the move as a swift and decisive response to North Korean behavior they said had gone far over the line. Never before has the U.S. imposed sanctions on another nation in direct retaliation for a cyberattack on an American company.“The order is not targeted at the people of North Korea, but rather is aimed at the government of North Korea and its activities that threaten the United States and others,” President Barack Obama wrote in a letter to House and Senate leaders.With this round of sanctions, the U.S. also put North Korea on notice that payback need not be limited to those who perpetrated the attack.The 10 North Koreans singled out for sanctions didn’t necessarily have anything to do with the attack on Sony, senior U.S. officials said.