WASHINGTON (AP) — President Donald Trump reiterated Thursday that military action is "certainly" an option against North Korea, as his administration tentatively concurred with the pariah nation's claim to have tested a hydrogen bomb.

A senior administration official said the U.S. was still assessing last weekend's underground explosion but so far noted nothing inconsistent with Pyongyang's claim.

If confirmed, that would mark a major advance in its demonstrated ability to build high-yield nuclear weapons. Hydrogen bombs have the potential to be far stronger than simpler fission bombs like tho...