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By Richie Duchon and Stella Kim

North Korea attempted a missile launch Wednesday morning but it failed almost immediately, U.S. military officials and South Korea said.

"A missile appears to have exploded within seconds of launch," U.S. Pacific Command spokesman Dave Benham said in a statement. "We are working with our interagency partners on a more detailed assessment. We continue to monitor North Korea's actions closely."

The launch comes a day after Kim Jong Un's regime issued an ominous warning of a potential pre-emptive strike after a test over the weekend of a new advanced rocket engine.

"The world will soon witness what eventful significance the … recent ground jet test of Korean-style high-thrust engine will carry," North Korea's Foreign Ministry said Tuesday via state-run news agency KCNA. "The nuclear force of [North Korea] is the treasured sword of justice and the most reliable war deterrence."

South Korea also confirmed the failed launch and said it was analyzing what type of missile was fired, a South Korean military official confirmed to NBC News.

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North Korea conducted two nuclear test explosions and 24 ballistic missile tests during 2016, and experts say it could have a nuclear-tipped missile capable of reaching the U.S. mainland within a few years.

Asked by NBC News' Andrea Mitchell whether North Korea's threat of pre-emptive military action represents a dangerous escalation, Secretary of State Rex Tillerson replied: "No comment today, thank you."

Andrea Mitchell contributed.