WASHINGTON (Reuters) - After nearly a year and a half in office, the Trump administration has succeeded in filling one of the most important U.S. diplomatic posts, with the Senate unanimously approving former Pacific commander Harry Harris as the next U.S. ambassador to South Korea.

FILE PHOTO: U.S. President Donald Trump arrives to receive a briefing from U.S. Navy Admiral Harry Harris (L), commander of United States Pacific Command, at its headquarters in Aiea, Hawaii, U.S. November 3, 2017. REUTERS/Jonathan Ernst

The Senate confirmed Harris’s nomination in a voice vote late on Thursday, and he is expected to take up his post in Seoul, which has been vacant since U.S. President Donald Trump’s January 2017 inauguration, in early July.

The retired admiral will take office at a time when South Korea and the United States are working closely together to engage with North Korea to try to persuade it to abandon a nuclear weapons program that now threatens the United States.

That engagement led to an unprecedented summit between Trump and North Korean leader Kim Jong Un on June 12, but protracted follow-on negotiations are expected to be needed before any concrete deal with Pyongyang.

Harris, who was born in Japan to a Japanese mother and American father, previously served as head of the U.S. Pacific Command in Hawaii, which includes the 28,500-strong U.S. force in South Korea, a key U.S. ally.

At a Senate hearing this month, Harris backed the idea of a “pause” in major U.S. military exercises with South Korea that Trump announced immediately after the summit. Harris said this would allow time “to see if Kim Jong Un is in fact serious about his part in negotiations.”

While handing over his command on May 30, Harris said North Korea remained the United States’ most imminent threat and said “a nuclear-capable North Korea with missiles that can reach the United States is unacceptable.”

Harris was initially nominated by Trump to be U.S. ambassador to Australia but was asked in April by Mike Pompeo, now secretary of state, to take the post in Seoul instead, as diplomatic efforts to resolve the North Korea crisis intensified.

Apart from North Korea, Harris will face a tricky task managing the U.S. trade relationship with South Korea, which Trump has repeatedly criticized as unfair. Trump has also at times questioned the usefulness of the long-standing U.S. alliance with South Korea and called on Seoul to pay more for the U.S. troop presence.

The Trump administration has been criticized by opponents for leaving key State Department positions unfilled, while the White House has blamed Democrats for blocking nominations.