The United States is confident it can stay ahead of North Korea's nuclear capabilities and is "absolutely committed" to preventing the communist nation from acquiring a nuclear weapon, a top U.S. defense official said.

    Deputy Secretary of Defense Robert Work made the remark during a House Armed Services Committee hearing on Thursday, stressing the importance of maintaining a strong nuclear deterrent force in the face of nuclear upgrades by Russia and China and the North's continued development of nuclear capabilities.

    "While we seek a world without nuclear weapons, we face the hard reality that Russia and China are rapidly modernizing their already-capable nuclear arsenals, and North Korea continues to develop nuclear weapons and the means to deliver them against the continental United States," Work said.

    "So a strong nuclear deterrent force will remain critical to our national security for the foreseeable future," he said.

    North Korea continues to expand its nuclear weapons and missile programs, the deputy secretary said, and in response the United States continues to improve its national missile defenses and conventional counter-force options.

    "We are absolutely confident that we can stay ahead of the capabilities that the North Koreans, and as the president said, we are absolutely committed to preventing them from acquiring a nuclear weapon," Work told the hearing.

    The North has conducted underground nuclear tests three times, in 2006, 2009 and 2013, and also built a facility to enrich uranium, which gives the communist regime a second way of building nuclear bombs in addition to its plutonium program.

    Six-party talks aimed at ending Pyongyang's nuclear program have been stalled since the last session in late 2008. North Korea has called for resuming negotiations without preconditions, but the U.S. has demanded Pyongyang first take concrete steps demonstrating its denuclearization commitments. (Yonhap)