The North Korea nuclear disarmament talks remain at an impasse in Beijing as Pyongyang refuses to give up its demand for a nuclear energy reactor. Meanwhile, Secretary of State Condoleezza Rice is warning that Washington may freeze North Korea's assets if no progress is made.

Speaking on day four of multination talks, chief U.S. negotiator Christopher Hill said attempts to get North Korea to focus on the goal of signing a joint statement on disarmament principles has gone no where.

"In fact, in the last couple of days, they have come back with a whole new concept. That is having a light-water reactor. So, indeed we have a problem," he said.

After four rounds of unsuccessful talks since 2003, North Korea this month began demanding the right to a peaceful nuclear program - causing the current impasse.

In a sign that patience is growing thin, Secretary of State Condoleezza Rice told the New York Post newspaper the United States is considering nonproliferation measures that could include freezing North Korean assets.

Washington has rejected the peaceful nuclear demand, saying Pyongyang could still turn the capability into a weapons program. U.S. officials says North Korea has a record of cheating on past agreements, which include withdrawing from the Non Proliferation Treaty, expelling U. N. monitors, and restarting its nuclear programs in violation of an agreement it signed with Washington in 1994.

Mr. Hill on Friday further defended the U.S. position, saying there exists no legal basis for any nation to provide North Korea, known also as the DPRK, with nuclear materials.

"The DPRK for the first time in the history of any country, pulled itself out of the nonproliferation treaty,"he said. "So, the DPRK put themselves in this position and has put themselves in a position where people cannot provide them with nuclear reactors or with such nuclear parts."

The issue has divided the United States from China, Russia, and South Korea - which have recently agreed that North Korea could have a peaceful nuclear capability if certain conditions are first met.

Mr. Hill has repeatedly urged the North Koreans to accept a proposal drafted by host China for a statement of principles. The draft includes offers of non-nuclear energy from South Korea, as well as economic aid and security guarantees.