DPRK ICBMs are not "a capable threat against us right now," Mattis said, during a news conference at the Pentagon, cited by CNN.
Mattis added that the Pentagon continues to weigh new surveillance on Pyongyang and its nuclear and missile capabilities.
"We are still examining the forensics, we're still doing the forensics analysis," he remarked, adding, "it takes a while."
Pyongyang boasted that it could land a nuclear warhead poised atop an ICBM anywhere in the US, following the November 28 launch of a high-altitude, far-ranging Hwasong-15 missile. Mattis, at the time, suggested that the DPRK was actively seeking the capability to deliver a nuclear warhead "everywhere in the world."
Mattis's Friday walkback of the threat posed by Pyongyang's nuclear missile development program is consistent, according to observers, of the technical analysis of North Korea's November launch, which American military experts suggest does not demonstrate that the DPRK has the ability to strike the US.
"I'm highly suspicious about the capability of the Hwasong-15," declared Atlantic Council senior fellow General Patrick O'Reilly (retired), an expert in missile defense, cited by CNN.
The November DPRK missile launch, according to O'Reilly, is said to have failed to achieve several key elements required to make a missile a credible threat, including stability, accuracy, and the capability to survive heat, vibration and reentry.
"There are some really ill-informed technical suppositions that have been made," O'Reilly stated, regarding the Hwasong-15 November launch.
The US aerospace expert asserted that the current threat posed by DPRK ICBMs is wrong, and is based on "very, very aggressive assumptions."
"There's a lot left to be done before you can assess a credible threat," he added.
US Secretary of Defense Mattis pointed to ongoing efforts by US Secretary of State Rex Tillerson to negotiate with Pyongyang, observing that diplomacy was the current Washington gambit, and adding that military options would take a back seat, for now.
"Diplomacy continues," the US Secretary of Defense remarked.