North Korea has denied an admission by Pakistan's top nuclear scientist that he sold nuclear weapons technology to the Communist state.
North Korea said it had shown its "nuclear deterrent" to a US team
A statement by a foreign ministry spokesman described the claim as "false propaganda" spread by the US, the state-run KCNA news agency said.
The spokesman said the "US smear campaign" justified Pyongyang's moves to build a "nuclear deterrent force".
It was North Korea's first official response to the Pakistani disclosures.
The denial comes before new talks between US, China, Japan, Russia and the two Koreas on Pyongyang's nuclear weapons programme in Beijing on 25 February.
Last week, the "father" of Pakistan's nuclear bomb, Abdul Qadeer Khan, publicly confessed he had sold nuclear secrets to North Korea, Iran and Libya through a black market.
Islamabad has pledged to fully co-operate with the UN nuclear watchdog, following strong US pressure on Pakistan to dismantle the secret nuclear trading network.
However, its ambassador to Washington, Ashraf Jehangir Qazi, told the BBC that Pakistan would not go beyond this and submit its weapons programme to international inspection.
"There is absolutely no need for any kind of intrusive measures," he said.
In an interview with the New York Times, President Pervez Musharraf of Pakistan said that he had suspected for at least three years that Dr Khan was sharing nuclear technology with other countries.
But he said that he needed proof and could not get that without the help of Washington.
"If they knew it earlier, they should have told us," the paper quotes the president as saying. "Maybe a lot of things would not have happened."
On Monday, US Secretary of State Colin Powell said he had urged President Pervez Musharraf to make sure that no more of the secret nuclear exchange network remained.
But the BBC's Paul Anderson in Islamabad says questions still remain:
How did those close to the country's nuclear programme not know what was happening under their noses?
Why does one of Pakistan's nuclear-capable missiles bear such a resemblance to a North Korean model?
North Korea has offered to freeze its programme in return for economic aid from Washington, but that only refers to its plutonium-producing facilities at the Yongbyon complex which may already have yielded enough weapons-grade material for a handful of atomic bombs.
It now strongly denies running a second secret programme based on the enrichment of uranium.
The US says it has evidence to the contrary and that the North admitted it when challenged in October 2002, in a confrontation which sparked the current crisis.
Khan was pardoned on condition he would co-operate with the inquiry
Pyongyang sees the revelations in Pakistan as an attempt by the US to bolster its allegations.
"This is nothing but mean and groundless propaganda," the North Korean spokesman said.
The US, he continued, was "hyping the story about the transfer of nuclear technology" to make North Korea's enriched uranium programme "sound plausible".
The ultimate aim, Pyongyang's spokesman said, was to scuttle this month's six-way talks and attack North Korea.
North Korea has said it has finished reprocessing 8,000 spent fuel rods being stored at Yongbyon - enough to help it build up to six nuclear weapons.
Last month, North Korea said it had shown its "nuclear deterrent" to an unofficial delegation from the United States.
The US team confirmed they had seen the secret nuclear complex that Washington believes is being used to develop nuclear weapons.