(CNN) The US admiral expected to become the country's next ambassador to South Korea says North Korea remains the most imminent threat to peace in the Pacific but China's "dream of hegemony" is Washington's biggest long-term challenge.

Adm. Harry Harris spoke Wednesday as he turned over the reins of the US Pacific Command to Adm. Phil Davidson at Pearl Harbor, Hawaii, in a ceremony that also announced the rebranding of US military assets in the region to the US Indo-Pacific Command.

Harris, who has been at the helm of the most expansive US military command for three years, hammered home points he's made repeatedly during his term.

Adm. Phil Davidson, left, relieves Adm. Harry Harris, right, as commander of US Indo-Pacific Command during a ceremony at Pearl Harbor, Hawaii, on Wednesday.

"North Korea remains our most imminent threat and a nuclear-capable North Korea with missiles that can reach the United States is unacceptable," he said.

However he added, "China remains our biggest long-term challenge. Without focused involvement and engagement by the United States and our allies and partners China will realize its dream of hegemony in Asia."

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