President Trump said "we'll see" on Sunday when asked whether the U.S. will attack North Korea.

Trump's comment follows the news that Pyongyang successfully tested a hydrogen bomb small enough to fit on a missile.

The president responded to North Korea's announcement on Twitter earlier on Sunday.

North Korea has conducted a major Nuclear Test. Their words and actions continue to be very hostile and dangerous to the United States..... — Donald J. Trump (@realDonaldTrump) September 3, 2017

..North Korea is a rogue nation which has become a great threat and embarrassment to China, which is trying to help but with little success. — Donald J. Trump (@realDonaldTrump) September 3, 2017

North Korea has advanced its aggressive military behavior in recent months, launching a series of intercontinental ballistic missiles.

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The United Nations Security Council unanimously voted in an effort led by the U.S. last month to impose tougher sanctions on North Korea as punishment.

Pyongyang launched a missile over Japanese airspace last week, signaling to the U.S. that it would not back off.

The president responded on Twitter, saying dialogue with North Korea was not an answer. Others in his administration have said the U.S. is "never out of diplomatic solutions."