US warships, including the supercarrier USS Carl Vinson and several guided-missile destroyers, have been diverted from a planned visit to Australia to Korean waters to safeguard American interests from a "reckless, irresponsible and destabilising" North Korea.
The Third Fleet's forward-deployed strike group was in Singapore and scheduled to sail to Australia for training and port calls.
The move comes as North Korean leader Kim Jong-un aggressively ramps up his ballistic missile test program.
It also follows US President Donald Trump's decision on Thursday to fire 59 Tomahawk missiles into a Syrian airfield to "send a message" to Syria President Bashar Al-Assad after chemical weapons were used on citizens in Idlib province.
"Third Fleet ships operate forward with a purpose: to safeguard US interests in the Western Pacific," said Commander Dave Benham, spokesman for the US Pacific Command.
"The number one threat in the region continues to be North Korea, due to its reckless, irresponsible, and destabilising program of missile tests and pursuit of a nuclear weapons capability."
North Korea launched a ballistic missile on Wednesday into the East Sea just ahead of Mr Trump's meeting in Florida with Chinese President Xi Jinping.
Watch: Japan and South Korea condemn North Korean aggression
North Korea's nuclear and missile programs were one of the top issues on the agenda, with China and its economic influence considered key to taming the North Korean dictator.
US Secretary Rex Tillerson said America's "policy of strategic patience has ended" with North Korea and "all options are on the table" while Australian Foreign Minister Julie Bishop has condemned North Korea for its "total disregard" of global security.
The USS Carl Vinson-led strike group's presence in the region will likely escalate tensions.
A supercarrier is the largest type of aircraft carrier.
"US Pacific Command ordered the Carl Vinson strike group north as a prudent measure to maintain readiness and presence in the Western Pacific," Commander Benham said.
