HONOLULU — The United States says its new round of sanctions against North Korea is just the opening salvo in its response to an unprecedented cyberattack on Sony. Yet there may be little else the U.S. can do to further isolate a country that already has few friends in the world.

Even the latest sanctions, handed down by President Barack Obama in an executive order, may not sting quite as badly as U.S. would have hoped. After all, North Korea is already under a strict sanctions regime imposed by the U.S. over the North’s nuclear program.

The new round of sanctions unveiled Friday hit three organizations closely tied to the North’s defense apparatus, plus 10 individuals who work for those groups or for North Korea’s government directly. Any assets they have in the U.S. will be frozen, and they’ll be barred from using the U.S. financial system.

But all three groups were already on the U.S. sanctions list, and officials couldn’t say whether any of the 10 individuals even have assets in the U.S. to freeze.

Still, 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.