The top U.S. envoy to the North Korea nuclear disarmament talks says diplomacy remains the best option to resolve the dispute. Christopher Hill met with Japanese officials Thursday on the final stop of Washington's latest diplomatic push to revive stalled negotiations to end North Korea's nuclear weapons program.

After meeting with Japanese officials Thursday, U.S. Assistant Secretary of State Christopher Hill said all options are being considered to get North Korea to abandon its nuclear ambitions. But the U.S. envoy stressed diplomacy is the best option and North Korea should return to six-nation talks.

"We still believe that the six-party process is the best way to solve this," he said. " So I don't want to speculate on what we might do if the six-party process is not able to solve this. But what I want to emphasize is that we're not going to walk away from this, we have to figure out a mechanism that works."

Diplomatic efforts by the United States, South Korea, Japan, Russia and China to disarm North Korea have dragged on for nearly two years without significant progress. Talks stalled in June after Pyongyang rejected an offer of possible energy aid and multilateral security assurances in exchange for ending its nuclear programs.

In February, Pyongyang announced it was abandoning multilateral talks and had developed nuclear weapons. Since then, North Korea repeatedly says it is enhancing its deterrent capabilities, accusing the United States of hostile intentions.

Pyongyang has recently shut down its Yongbyon nuclear reactor, a move that analysts say would allow the extraction of plutonium for additional fuel to build nuclear weapons.

U.S. Secretary of State Condoleezza Rice said earlier this week that Washington reserves the right at any time to refer the issue to the U.N. Security Council for actions. Such actions could include sanctions or a sea blockade to intercept shipments that might contain nuclear-related materials.

Mr. Hill's trip to Japan follows similar consultations with Chinese and South Korean officials earlier this week.