SYDNEY, Australia — President Trump has said he plans to nominate Adm. Harry B. Harris Jr., the commander of the United States Pacific Command and a vocal critic of China’s military expansion in the region, as ambassador to Australia.

Admiral Harris, 61, who has spent 39 years in the Navy, is expected to easily win confirmation in the Senate.

The United States has been without an ambassador to Australia, a major ally, since 2016. The alliance between the countries was strained in the early days of the Trump administration by an argument between President Trump and Prime Minister Malcolm Turnbull over the resettlement of refugees.

As China flexes its might and North Korea speeds its nuclear program, a strong alliance between the United States and Australia is seen by many as crucial to maintaining the balance of power in the Asia-Pacific region.