Wormuth, who now serves as a senior adviser at the Center for Strategic and International Studies in Washington, agrees that North Korea is becoming a more serious challenge with each missile test, whether successful or failed.
Trump and Pence, who stopped at the Demilitarized Zone dividing North and South Korea on Monday, have signaled this week a forceful US stance on North Korea's recent actions. The new version has an improved booster and warhead.
"If we notice any sign of assault on our sovereignty, our army will launch merciless military strikes against the USA aggressors, wherever they may exist, from the remote USA lands to the American military bases on the Korean Peninsula, such as those of Japan and elsewhere".
North Korea said in February that it had successfully tested a new type of medium- to long-range ballistic missile, the Pukkuksong-2, propelled by a solid-fuel engine.
But reports since have indicated that Washington's new policy towards the DPRK will focus on maximum pressure and engagement.
In the upcoming test, a missile will be launched from the Vandenberg Air Force Base in California and attempt to intercept a simulated missile over the Pacific Ocean.
He said Trump is certain that negotiating trade deals with individual countries was the best way to ensure they yield "win-win" situations for both sides.
South Korea's acting president, Hwang Kyo-ahn, at a meeting with top officials on Thursday, repeatedly called for the military and security ministries to maintain vigilance.
The official emphasized that all of the ongoing work doesn't change the administration - and Pentagon's - emphasis on the need for a peaceful diplomatic solution. "We're not going to remove the military tool from our toolkit, '" Nau said.
While the US will continue to pursue diplomatic solutions, any conventional or nuclear attack by an enemy would be defeated "with an overwhelming and effective American response", Pence told the crowd aboard the ship Wednesday. Multiple US officials said all current anti-missile ships and other ground-based interceptors in Alaska are available.
The military has not made a decision to intercept a test missile but the United States defense secretary James Mattis has briefed Congress on the option.
Mattis denounced North Korea's attempted missile launch as he began a Middle East tour, telling reporters traveling with him to Saudi Arabia, "the leader of North Korea again recklessly tried to provoke something by launching a missile", he said. "But I think that our understanding is that it was not one of the longer-range missiles that they were trying to test there; it was something like a medium-range ballistic missile".
Pence made an unannounced visit to the Demilitarized Zone at the start of his 10-day trip to Asia in a USA show of force that allowed the vice president to gaze at North Korean soldiers from afar and stare directly across a border marked by razor wire.