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Story highlights

The US says North Korea now poses a "practical" rather than "theoretical" threat

North Korea no longer cares if the world sees its tests as failures

(CNN) —  

The US government is increasingly concerned that advances in North Korea’s weapons program have dramatically decreased the warning time for a nuclear attack on America or its allies, according to US officials.

The regime’s aggressive testing of medium- and long-range missiles – as well as its nuclear testing – makes North Korea now a “practical” threat and no longer a “theoretical” threat, in the words of one US official familiar with the latest US intelligence thinking.

Significantly, North Korea no longer cares if the world sees its test failures, according to the latest analyses, allowing Pyongyang to more openly, aggressively and repeatedly test all of the key components needed for an attack.

RELATED: Kim Jong Un: We’ll only use nuclear weapons if sovereignty threatened

As a result, the regime has the ability to hold the US and allies “at risk” with nuclear weapons, the US official said.

“When you have this many tests, you are eventually going to get it right. That’s what concerns me,” said retired Lt. Gen. Mark Hertling, a CNN military analyst. “As soon as they have one test that they could classify as an extreme success, then we are talking a whole different ballgame (in) their potential to threaten other sovereign nations in their area but also potentially parts of the United States.”

At this point, the US now works on the assumption North Korea has achieved warhead miniaturization – essential for a missile attack.

RELATED: North Korea claims missile test success

New satellites images from the 38 North website reveal activity at North Korea’s nuclear test site, showing a canopy has been erected to block the view of US spy satellites.

And in recent missile tests, North Korea has fired: mobile missiles that are difficult to track, submarine launched missiles, also difficult to track, and intercontinental missiles that can potentially reach Alaska.

The bottom line, officials said, is with small warheads, road-mobile missiles and sub-launched missiles, there is no early warning.

Most concerning, they said, is the recent intermediate-range launch went within 150 miles of Japan coastline – just a few seconds of flight.