U.S. nuclear negotiator Christopher Hill says the six-party agreement on North Korea's denuclearization can progress quickly and even reach the critical phase of disabling the North's key nuclear facilities by year's end.

Hill declared Friday that disabling the facilities can be done "in a matter of weeks, not months."

Hill's comments come amid continuing frustration over stalled progress on the deal struck February 13th by South and North Korea, the U.S., China, Russia and Japan. The accord requires as first-phase implementation steps that Pyongyang shut down its primary nuclear facilities and open itself to international inspections within 60 days.

But the April 14th deadline passed without action by the North, which insisted that it must first be able to access 25 million dollars previously frozen by a Macao bank. The funds were released last month, but technical difficulties have prevented their transfer.

Under the action-for-action principle, Pyongyang is to receive fuel and other aid in return for fulfilling its first-phase commitments. Second-phase implementation requires the North to declare all its nuclear programs and disable all related facilities.

The U.S. official dispelled growing skepticism about February's six-party deal, saying that he believes North Korea is committed to the agreement.