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North Korea threatened Thursday to use the delay in six-party nuclear talks to bolster its military "deterrent force," a phrase the isolated communist nation often evokes in reference to its nuclear weapons program.

"It's not bad that the resumption of nuclear talks are delayed. During that period, we will make more deterrent force," said North's top nuclear envoy Kim Kye Gwan, speaking at a news conference in Tokyo. "We will react in an ultra hardline manner if the United States continues to apply pressure and sanctions. We will never yield to pressure."

Kim added, however, that North Korea would be willing to return to international nuclear talks, aimed at ending North Korea's nuclear weapons program, if the United States lifts a freeze on disputed North Korean assets in a Macau bank.

North Korea has refused to restart the talks unless the financial restrictions — imposed on a Macau bank and North Korean companies — are lifted, but Washington has maintained the sanctions are unrelated to the nuclear talks and will stay in place.

The assets total about $24 million, which Washington says is linked to money laundering and counterfeiting.

U.S. Assistant Secretary of State Christopher Hill, in Seoul for separate talks Thursday, said Washington won't relax the restrictions unless Pyongyang gives up its pursuit of nuclear arms.

"The DPRK needs to understand that as long as it's going to be producing nuclear weapons, we're going to have a really close look at the finances," Hill said in a speech to a U.S. business group.

DPRK stands for the North's official name, the Democratic People's Republic of Korea.

Regarding financial sanctions, Kim said, "There is no compromise and flexibility on this issue." He added: "I will go to the negotiating table the moment I seize the assets with my hands."

Kim said his country understands the U.S. campaign against counterfeiting and money laundering and is prepared to cooperate with Washington but lashed out at the United States for taking advantage of Pyongyang's commitment to help.

In February, the North pledged to join international efforts to fight money laundering, but it has denied accusations the regime is directly involved in financial crimes.

Kim's comments wrap up several days of nuclear talks between the six nations trying to negotiate North Korea's nuclear disarmament — the United States, China, Japan, Russia and the two Koreas. The barrage of diplomatic meetings in Japan, however, failed to win a commitment from North Korea to return to the stalled talks.

After the Tokyo discussions, Chinese chief negotiator Wu Dawei said there was no possibility of resuming talks by the end of April, saying the sanction issue was the chief stumbling block.

"We'll continue to make efforts," Wu said. "At the moment, our prospects are still unclear."

This week's security meetings had raised hopes about the possibility of restarting talks that have been stalled since last year on ending North Korea's nuclear program in exchange for aid. Pyongyang has boycotted the six-party nuclear talks since November.