The State Department on Friday disputed a U.S. official's assertion that North Korea (search) had threatened to test a nuclear weapon (searchunless the United States accepted its terms for a freeze.

The negotiators in Beijing are exchanging proposals that will be considered in the six nations' capitals after a recess is declared on Saturday, department spokesman Adam Ereli said.

He described the atmosphere at the talks, which included a 2 1/2-hour session Thursday between the United States and North Korea, as constructive.

"The parties have been earnest in exploring the various proposals put forward," Ereli said. "We expect this process to continue, following the closing of the talks tomorrow."

In Beijing earlier, a U.S. official who insisted on not being identified by name or position told reporters North Korea had threatened to test a nuclear weapons unless the United States accepted its conditions for a freeze on nuclear programs, thereby jeopardizing the negotiations.

North Korea is asking for energy assistance (search) in exchange for a freeze, and the United States is known to be receptive to having Japan and South Korea provide aid if the nuclear weapons program is halted.

Also, President Bush has held out the offer of a promise not to attack North Korea, which he had declared to be part of an "axis of evil."

"There's been a lot written about the issue of a threat from the North Koreans to test," Ereli said. "There have been a variety of quotes in the press. I would say on the record that the remarks that are being reported were not phrased as a threat, No. 1. It was phrased as a statement that some in Pyongyang wanted to test a nuclear weapon."

Ereli added: "This is not something new. We've heard these sort of comments before. It was not phrased or given as an ultimatum, but rather, to the contrary, I think we came away from this discussion, from this long and involved and engaged discussion, with the firm view that the North Koreans are going to give our proposal very serious consideration."

After the current round "there needs to be period of reflection" before setting a date for the next round, the spokesman said.

Ereli said the United States remained committed to "denuclearization" of the Korean peninsula.

At the six-nation talks with the United States and North Korea are China, Japan, South Korea and Russia.

The negotiations were begun last August and appeared to be making little progress until the current round. Secretary of State Colin Powell this week said the talks were being conducted "in a spirit of flexibility."