State Department spokesman Sean McCormack told reporters that North Korea has been "getting closer and closer" to the point where it will restart the reactor but has not gotten there yet.
"We would urge them not to get to that point," he said.
The North did not say when the reactor might begin operating again. The comments marked the first time the North has confirmed a reversal of steps taken since last year to disable its nuclear program. North Korea is angry over Washington's refusal to quickly remove it from a U.S. terrorism blacklist.
Asked why the North should deal with the Bush administration since it is in its final months in office, McCormack said, "I don't know who the next president, who the next secretary of state is going to be, but I would wager that they're not going to get a much different deal from the next administration as they're getting from this administration."
He also noted existing U.N. Security Council resolutions "that hold penalties for North Korea should they go down the pathway of, for example, missile testing, for example, further testing of any nuclear devices."
Under a 2007 pact, North Korea pledged to disable its nuclear program as a step toward its eventual dismantlement in exchange for diplomatic concessions and energy aid.
In late June, North Korea submitted a long-delayed declaration of its nuclear activities and destroyed the cooling tower at Yongbyon in a show of its commitment to the nuclear deal. But the accord stalled in mid-August when Washington refused to take North Korea off its list of states that sponsor terrorism. The U.S. says the North first must accept a plan to verify its nuclear declaration.
McCormack said the United States and other members of the six nation negotiations continue to talk with North Korean officials.
The North, he said, has "a choice. They can go down the pathway of having a different kind of relationship with the rest of the world, receiving the benefits of that relationship, or they can keep themselves isolated, move the process backward."
