WASHINGTON (Yonhap) -- U.S. Defense Secretary Leon Panetta expressed concern Thursday that North Korea might have mastered a mobile ability for long-range missiles.

"There is growing concern about, you know, the mobile capabilities that were on display on the parade activity in North Korea," he said at a congressional hearing.

The North showed off what appeared to be a new long-range missile on a 16-wheel vehicle during the parade on Sunday in front of foreign reporters and television crews.

Experts are split over its ramifications. Some say it seems to be a new intercontinental ballistic missile, while others dismiss it as a life-size mockup.

Panetta said U.S. intelligence agencies are trying to get more information.

"If they in fact have a mobile capability" for intercontinental ballistic missiles, the potential threat from North Korea is increased, Panetta told the House Armed Services Committee.

The U.S. hopes that North Korea will not take additional provocative steps after a failed long-range rocket launch.

"We're prepared from the Defense Department's point of view to deal with any contingency," Panetta said.