A US Navy strike group was moving toward the Korean Peninsula on Saturday, the US military confirmed, as the United States boosts its defenses against North Korea's growing nuclear ambitions.

"US Pacific Command ordered the Carl Vinson Strike Group north as a prudent measure to maintain readiness and presence in the Western Pacific," said Commander Dave Benham, a US Pacific Command spokesman.

"The number one threat in the region continues to be North Korea, due to its reckless, irresponsible and destabilizing program of missile tests and pursuit of a nuclear weapons capability," he told AFP.