The United States and other nations that took part in talks on the North Korean nuclear crisis are calling the meeting in Beijing a positive first step, and are looking forward to a second round of talks. But North Korea is now calling the talks "useless," and saying it has no choice but to strengthen its "nuclear deterrent."

The North Korean threat came in a statement from the Foreign Ministry, carried by the country's official news agency on Saturday.

A Foreign Ministry spokesman was quoted as calling the three-day talks in Beijing, which ended Friday, "not only useless, but harmful."

The statement followed similar remarks Saturday by one of the North Korean delegates, as his group left Beijing for home.

The Foreign Ministry statement accused the participants, including the United States, of using this week's talks to force the North into disarming. The statement said Pyongyang believes it has no alternative but to bolster its defenses by continuing to develop what the statement referred to as its "nuclear deterrent."

During the talks, the North Koreans said they already possessed nuclear weapons, and were quoted by other delegates as threatening to carry out a nuclear test.

The aim of the six-nation talks is to persuade the North to end its nuclear program. China, the host for the talks, announced Friday that all parties had agreed to a second round about two months from now, which was taken as a positive sign, but Saturday's remarks by the North Koreans raised doubts about that.

However, one Western diplomat in Beijing characterized the North Korean remarks as blustering on Pyongyang's part, the type of comments the communist country has traditionally employed during lengthy negotiations.

That assessment was echoed by David Zweig, a political science professor at Hong Kong's University of Science and Technology. He said that despite the comments, North Korean officials probably believe it is in their best interest to keep negotiating.

"My own view is that they actually want a deal," he said. "They may be afraid that the Americans are not going to come forward with any kind of movement on this and that they are just going to hold their position. And the way they believe that you would pressure the Americans to make some concessions is to threaten to blow the whole thing wide open."

Saying it fears an attack by the United States, North Korea's main demand has been for Washington to sign a non-aggression pact. The United States has ruled out a formal treaty, although it says it will give written assurances that it will not attack the North. However, Washington says North Korea first must dismantle its nuclear program in a verifiable manner.

The three days of discussions were an opportunity for all six nations to present their views. The delegates are now returning to their countries for consultations on how to proceed when the talks reconvene.

The head of the U.S. delegation to the talks, Assistant Secretary of State James Kelly, left Beijing Saturday calling the discussions a "productive start." Other participants also labeled the meeting a good first step toward ending the 10-month-old nuclear crisis.