Defense Secretary nominee Mark Esper testifies before a Senate Armed Services Committee hearing on his nomination in Washington, U.S. July 16, 2019. REUTERS/Erin Scott

WASHINGTON (Reuters) - U.S. President Donald Trump’s nominee to become the next secretary of defense called Turkey’s decision to buy Russia’s S-400 air defense system “disappointing,” in remarks that break days of administration silence about the move by the NATO ally.

“They have been a long standing and very capable NATO ally, but their decision on the S-400 is the wrong one and it is disappointing,” said Army Secretary Mark Esper, testifying on Tuesday before the Senate Armed Services Committee.

Esper returned to his Army role after stepping down as acting defense secretary while the Senate weighs his nomination.