North Korea (searchangrily dismissed the possibility of further negotiations over its nuclear program on Saturday, one day after the end of landmark six-nation talks where the isolated regime indicated it might be willing to reach a compromise.

"This round of talks was nothing more than empty talks," an unidentified North Korean delegation spokesman told reporters at the airport, reading from a statement as the envoys were leaving Beijing.

"We no longer have interest, or expectations either, for this kind of talks," he said. "We are left with no option."

Less than two hours earlier, Assistant Secretary of State James Kelly (search), who represented the United States in the talks, said all parties had gotten off to "a productive start."

The U.S. Embassy in Beijing said it had no immediate comment on the North Korean delegation's remarks. The Chinese and South Korean governments did not immediately react either.

In Tokyo, Japan's Defense Agency unveiled plans to seek $1.2 billion for U.S.-designed systems to defend against ballistic missiles. The request is part of a major defense initiative spawned by concern over North Korea's long-range missiles.

The agency's annual budget proposal calls for buying two U.S.-developed weapons systems -- one sea-based and one land-based -- to provide a double shield against missiles with a range of up to 600 miles. Delivery could start as early as 2006.

Japan has been conducting joint research with the United States on missile defense since 1999 -- a year after the test-launch of a three-stage North Korean Taepodong missile (searchthat flew over Japanese airspace. The incident showed that virtually all of Japan could be targeted by North Korean missiles.

This week's extraordinary three-day, six-country summit was the result of months of delicate political maneuvering. China, the North's last major ally, also played host to diplomats from Japan, South Korea and Russia.

Tensions have been growing since October, when Pyongyang acknowledged privately to Kelly that it had restarted its nuclear weapons program.

The United States has insisted on "the complete, verifiable and irreversible elimination" of North Korea's nuclear weapons program before it can seriously consider improving relations with the North. But the impoverished Stalinist regime has refused to comply without security and economic aid guarantees.

All the governments represented at the Beijing talks had expressed varying degrees of opposition to the North's nuclear ambitions. China has also said repeatedly that it wants a nuclear-free Korean Peninsula.

The delegates from the six countries said the main goal of the gathering was to establish an opening for future talks and address North Korea's security issues. No date or venue was established, but China Central Television reported that fresh meetings would take place within two months.

"We've had a nice visit to Beijing, a productive start," Kelly told reporters before leaving for the airport. "We've got a very long way to travel."

He added: "But a peaceful solution is something we're going to work on."

Kelly and his delegation met with their North Korean counterparts on Wednesday along the sidelines of the summit, which began on an amicable note as delegates smiled, shook hands and posed for photos. Kelly and Pyongyang's chief delegate, Vice Foreign Minister Kim Yong Il, shook hands with each other before turning to the others.

The informal huddle was the first direct contact between the United States and North Korea since April, when Beijing hosted their meetings on the issue.

The brinkmanship and bluster that has characterized North Korea's diplomacy surfaced on the second day, when North Korea said it would prove to the world it possesses nuclear weapons by testing a nuclear device, according to a U.S. official who spoke on condition of anonymity.

In Washington, State Department press officer Jo-Anne Prokopowicz said Friday that the threats "are not a surprise."

"The U.S. will not respond to threats or give in to blackmail," she said. "These threats only serve to further isolate North Korea from the international community."

But Kim also showed a willingness to compromise, suggesting that his country would abandon the nuclear weapons program if the United States agreed to its conditions.

"It is not our goal to have nuclear weapons," Pyongyang's state-run news agency, KCNA, quoted Kim as saying.

The delegation spokesman at the airport, however, reverted back to North's original rhetoric.

"This is not just a difference in opinion but a difference in fundamental policies," the North Korean delegation spokesman said. "We have come to conclude that the United States has no intention for a policy switchover and it plots to disarm our country through sinister schemes."

Also Saturday, North Korea's state-run newspaper Minju Joson said its "nuclear deterrent force" is a self-defense measure to cope with what they called U.S. strategy to "stifle" its communist country.

"Our nuclear deterrent force is a self-defense measure to cope with the U.S. strategy to isolate and stifle the DPRK," the newspaper said, according to South Korea's Yonhap news agency.