The US says it will stop giving food aid to North Korea unless it lets international relief workers monitor its distribution.
North Korea says better harvests mean it no longer needs food aid
The US said it wanted to check aid - channelled through the UN's World Food Programme (WFP) - reached the needy.
The statement comes as the WFP prepares to halt food aid to North Korea after Pyongyang said it was no longer needed.
US-N Korean relations have been deteriorating since September talks on ending the North's nuclear ambitions.
North Korea has relied on foreign aid to feed millions of people since acknowledging a serious famine in the mid-1990s.
But it now says better harvests at home and aid supplies from China and South Korea have rendered the aid distributed by the UN redundant.
Instead, Pyongyang has said it wants more foreign help with long-term development projects.
'Policy of starvation'
The US is one of the biggest donors to the WFP, which has overseen the distribution of food aid in North Korea.
In June, it promised 50,000 tonnes of food aid would be delivered - though the WFP - after saying that better monitoring on the part of the WFP and more cooperation on the part of North Korea had reduced the chance of aid being diverted
But now US State Department Spokesman Adam Ereli has warned the aid might be the last.
Mr Ereli said more aid had been earmarked for North Korea but would not be released until Pyongyang allowed its distribution to be better monitored.
"Until and unless we can be sure that the food we give is really going to the people who need it, then we can't continue to provide aid," he said.
But, he said, criteria for monitoring were not being met.
Mr Ereli accused Pyongyang of ignoring the needs of its people and letting them starve for "inexplicable reasons".
By the end of 2005, the WFP will have wound down a programme that, at its peak, was feeding some 6.5 million North Koreans.
The UN food agency says the famine is now over but some 37% of North Korean children remain chronically malnourished, according to a survey it conducted in 2004.
Talks on what form the WFP's presence in North Korea may take in the future ended earlier this month, with the agency saying it hoped to eventually re-instate parts of its programme.