The first international talks on North Korea's nuclear program since the communist nation tested an atomic bomb ended Friday with Pyongyang vowing to bolster its arsenal in response to U.S. pressure.

The five days of negotiations finished without any further meetings scheduled as the delegates merely reaffirmed a September 2005 joint statement — the only one ever reached at the talks — in which the North pledged to disarm in exchange for security guarantees and aid, Chinese envoy Wu Dawei said.

During three years of the six-nation talks, the North has never taken any concrete steps to dismantle its nuclear program, instead continuing to operate its main reactor to create weapons-grade plutonium and conducting its first atomic test Oct. 9.

Asked if North Korea would conduct further nuclear tests, envoy Kim Kye Gwan said Pyongyang was working to enhance its atomic capabilities.

Monitor the nuclear showdown on the Korean Peninsula in FOXNews.com's North Korea Center.

"The U.S. is taking a tactic of both dialogue and pressure, and carrots and sticks," he told reporters. "We are responding with dialogue and a shield. And by a shield, we are saying we will further improve our deterrent."

The North had ended its 13-month boycott of the talks — which include China, Japan, Russia and South Korea — after the U.S. agreed to discuss its campaign to isolate the communist nation from the international financial system for alleged financial crimes, including counterfeiting and money laundering.

Separate talks this week on that issue in Beijing failed to bridge differences between the sides.

Other negotiators said Pyongyang refused to talk about its nuclear weapons program, and instead stuck to its demand that the U.S. remove the financial restrictions it has imposed on the regime.

"We have requested the U.S. to release the sanctions first and then go into a discussion on substantive issues for the implementation" of the September 2005 agreement, Kim said.

"How can (North Korea) go into such an important discussion on halting the nuclear facilities and also giving up the deterrent which is aimed at safeguarding our sovereignty under such pressure from the United States?" Kim asked.

Even when it takes up the nuclear issue, Kim said the North wouldn't immediately talk about dismantling the bombs it has already made. But he promised the North won't launch a nuclear attack or sell its atomic technology.

"Since we are already a proud nuclear state, we have already announced that we will not threaten other countries with nuclear (weapons) and fully live up to our responsibility of preventing proliferation," Kim said.

China's Wu said the six countries agreed to meet again "at the earliest opportunity."

The main U.S. envoy said the talks would reconvene in "weeks, not months."

Assistant Secretary of State Christopher Hill said that he had expected more from the North Koreans, but that it appeared the Pyongyang regime hadn't given their negotiators any authority to discuss anything but the financial issue.

"Clearly, negotiators ought to come armed with some instructions to negotiate," he said Friday evening.

Hill insisted the talks wouldn't be left in limbo for another 13 months, and that Washington remained committed to resolving the issue in the six-nation format.

"We have to make progress — we should have made that progress this week," he said.

"North Korea lost a very important opportunity," said Japanese envoy Kenichiro Sasae. "We find the North Korean attitude extremely regrettable."

Sasae said Pyongyang risked further isolation from the international community if it did not change its stance.

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