As Japan, the United States and South Korea meet in Tokyo to discuss setting up a second round of international talks on halting North Korea's nuclear weapons development, Pyongyang warns that it is already taking steps to increase it nuclear capabilities.

North Korea is once again saying that it has no interest in further rounds of six-party talks on its nuclear program, echoing comments made following the first such round, which was held in Beijing in August and ended without concrete progress.

The north also says it is boosting its nuclear capabilities as a deterrent against a possible attack by the United States. For weeks, Pyongyang, through its Korean Central News Agency, has threatened to beef up nuclear weapons development to ward off a possible U.S. strike.

A spokesman of the North Korean Foreign Ministry said that if Washington pushed the north to give up its nuclear weapons program before guaranteeing the isolated Stalinist state's security, it could lead to war.

The South Korean and American governments see such comments as a typical North Korean negotiating tactic.

Pyongyang also called again for a non-aggression treaty from the United States before it responds to international concerns about its nuclear program, a request Washington has repeatedly rejected. The United States insists the north must scrap its weapons programs first, but has also said it has no plans to attack it.

The north's latest commentary comes as the Bush administration's top negotiator on North Korea, Assistant Secretary of State James Kelly, met for a second day with officials from Japan and South Korea in Tokyo to discuss preparations for a new round of six-country talks involving China, Russia, the two Koreas, Japan and the United States.

The talks were held behind closed doors at a Tokyo hotel and officials did not comment on the meeting's content.

Noriyuki Suzuki, a Japan-based North Korea expert, says he has high hopes for the six-party process and noted that all participants agreed to work on solving the conflict peacefully. He added that he is confident that the negotiation process will eventually halt North Korea's nuclear activities.

Also Tuesday, the United States and South Korea commemorated the 50th anniversary of their Mutual Defense Treaty, under which Washington stations 37,000 U.S. troops in South Korea to help protect it in case the North launches an attack.

The American ambassador to South Korea, Thomas Hubbard, said in a speech in Seoul on Tuesday that the United States and South Korea must continue to be vigilant in the face of the North Korean security threat.

The nuclear crisis erupted nearly one year ago when the United States accused North Korea of the reneging on a 1994 agreement by running a secret nuclear weapons program.