US Army Gen. Mark A. Milley testifies before the Senate Armed Services Committee on his nomination to be chairman of the Joint Chiefs of Staff, on Capitol Hill July 11, 2019 in Washington, DC.
CNN  — 

The Senate Thursday overwhelmingly voted 89 to 1 to confirm President Donald Trump’s pick to be the next chairman of the Joint Chiefs of Staff, Gen. Mark Milley.

Milley is currently serving as chief of staff of the Army.

“I am humbled and honored to be confirmed as the next Chairman of the Joint Chiefs of Staff,” Milley said in a statement following the vote.

“Thank you to the President and the Senate for their confidence,” he added.

The chairman is the highest-ranking military officer in the country and serves as the principal military adviser to the President.

The lone dissenting senator was Democrat Jeff Merkley of Oregon. A spokesman for Merkley told CNN that the senator “was concerned by Gen. Milley’s stated support for building up the US’s nuclear arsenal and deployments” and “voted no accordingly.”

The current chairman of the Joint Chiefs, Gen. Joseph Dunford, who took on the role in 2015, is expected to serve out the remainder of his term which will finish at the end of September.

“Congratulations to Gen. Mark Milley on his Senate confirmation to be the next Chairman of the Joint Chiefs of Staff,” Dunford said in a statement Thursday.

“Gen. Milley and I have served together multiple times to include our time together in combat. He will be a superb Chairman,” he added.

Trump took the unusual step of announcing his pick to replace Dunford on Twitter back in December, nearly a year before the end of his term.

On Tuesday the Senate voted overwhelmingly 90 to 8 to confirm Trump’s pick for secretary of defense, Mark Esper.

Milley will be stepping into the job as the military works to confront a variety of challenges ranging from Iran to counter-terrorism campaigns in Iraq, Afghanistan and Syria as the Pentagon seeks to shift focus on nation-state competitors like Russia and China.

Milley recently warned that China could pose a threat to the US for the rest of the century.

He has held numerous command and leadership positions, including in the Army’s Special Forces, and has deployed numerous times, including serving overseas in Iraq, Afghanistan, Somalia, Bosnia-Herzegovina and Panama.

A native of Massachusetts, Milley holds degrees from Princeton University and Columbia University.

If confirmed, Milley will be the first chairman of the Joint Chiefs of Staff to serve a single four-year term, a new policy made law in 2017.

CNN’s Zachary Cohen contributed to this report.