North Korea's nuclear and missile programs have moved forward faster than expected, especially since the transition of leadership a year ago, a top U.S. military commander told lawmakers Wednesday.

"I think that North Korea proceeded at a pace faster than we had anticipated," Army Gen. Charles Jacoby, head of the U.S. Northern Command, said at a hearing of the House Armed Services Committee.

His command is tasked with managing the operation of the U.S. homeland missile defense system.

Among many factors are, he said, the change in leadership in the communist nation over the past year.

Kim Jong-un, reportedly in his late 20s, seized control of the traditionally unpredictable nation shortly after the death of his father, Kim Jong-il, in December 2011.

Many observers say although he is inexperienced, the junior Kim appears to be seeking a bolder or more aggressive strategy than his father.

Under his leadership, Pyongyang fired a long-range rocket last April, which ended up in a failure, but made a successful attempt to put a satellite into orbit in December. In January, it carried out a nuclear test in a series of fast-moving provocations.

The U.S. government has apparently taken the North's threats more seriously.

Last week, the Obama administration reversed its decision to shelve plans to add 14 ground-based interceptor (GBI) missiles to its homeland defense networks.

The Pentagon cited increasing threats from North Korea behind the move.

It added it is also conducting environmental impact studies for a potential GBI site on the East Coast.

Currently, the U.S. has a total of 30 GBIs in Alaska and Florida.

"I think we are on a good path to outpace the threat, both North Korean and Iranian threats in the future," Jacoby said. "I would agree that a third site, wherever the decision is to build a third site, would give me better weapon access, increased GBI inventory and allow us the battle space to more optimize our defense against future threats from Iran and North Korea."

Still, many question the effectiveness of the U.S. missile shield.

Jacoby said the U.S. military is trying to hone the so-called "shoot-look-shoot" ability of the GBIs.

He was referring to a tactic to assure a kill by shooting at the target, looking to see if it was killed, and shooting again if necessary to achieve the kill.

"Shooting down a ballistic missile is a sniper weapon requirement," he said. "It's not a machine gun requirement. So we want to pursue shoot-look- shoot, not just for North Korea but as a war fighter technique." (Yonhap News)