WASHINGTON (AP) — Nations including China and Russia that launch cyberattacks against the U.S. don't fear retribution and see no reason to change their behavior, the Army officer tapped to be the next head of U.S. Cyber Command told a Senate Committee Thursday.

Army Lt. Gen. Paul M. Nakasone said that cyber threats against the country have grown exponentially, and the U.S. must impose costs on those adversaries to make them stop.

Frustrated members of the Senate Armed Services Committee peppered Nakasone with questions about what the U.S. should do to nations that infiltrate government ne...