WASHINGTON — The U.S. has seen no need to shoot down North Korean missiles test-fired in Japan’s direction, but a future missile launch that threatens U.S. or Japanese territory will “elicit a different response from us,” Defense Secretary Jim Mattis said Monday.

He also said, without elaboration, that the Trump administration has military options against North Korea that would not put Seoul at risk. He would not say whether he was referring to overt combat action, a cyberattack or something more covert.

“I will not go into details,” he said.

Mattis also confirmed that he and his South Korean counterpart had recently discussed the possibility of putting U.S. nuclear weapons back into South Korea, an option that has been raised publicly by some South Korean politicians. U.S. nuclear weapons were withdrawn from the Korean peninsula in the early 1990s at the close of the Cold War.

“We discussed the option, but that’s all … I want to say,” he said.