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President Donald Trump said Wednesday he would be "very, very disappointed" if North Korea is rebuilding a long-range rocket site at Sohae that had been dormant since last summer.

Responding to a question about an NBC News story on North Korea rapidly rebuilding part of the Sohae Satellite Launch facility, Trump said “it’s too early to see” if North Korea is breaking a promise to dismantle the site.

In his brief remarks, Trump called the situation with North Korea a "very nasty problem," but expressed optimism that the situation will be resolved.

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"The relationship is good," Trump said. "I would be very disappointed if that were happening. It's a very early report. We're the ones that put it out, but I would be very, very disappointed in Chairman Kim and I don't think I will be, but we'll see what happens. We'll take a look. It'll ultimately get solved."

The Trump administration did not put out the report.

Trump's comments came a day after NBC News reported that analysts at Beyond Parallel, a research project sponsored by the defense think tank Center for Strategic and International Studies, acquired commercial satellite imagery showing increased activity at the site that is "consistent with preparations for a test."

The site, North Korea's only operational space launch facility, has been used in the past for satellite launches. These launches use similar technology to what is used for intercontinental ballistic missiles.

"Current activity is deliberate and purposeful," authors Joseph S. Bermudez and Victor Cha wrote. The activity is "evident at the vertical engine test stand and the launch pad's rail mounted rocket transfer structure."

But the analysts cautioned that the imagery has yet to show a missile being moved to the launch pad.

In an interview with NBC News, Cha said the North Koreans may be trying to send Trump a message after talks between the American president and his counterpart Kim Jong Un broke down in Vietnam last week.

"It's entirely possible that they know we are watching this and they may be sending a signal," Cha said. "There is no activity at this site since August of 2018 and certainly no activity before the Hanoi summit, so to start up this activity only 48 hours after the failed summit is a clear sign that they're angry and that they want to send a message to President Trump."

The North Koreans began to dismantle some facilities at Sohae after the first summit between the two leaders in Singapore in June 2018, according to Beyond Parallel.