Tony Hall, Rome-based US ambassador to the UN food agencies, said the United States was pushing to tighten monitoring of UN food aid distribution in North Korea.
The UN World Food Programme (WFP), the world's biggest food aid agency, said it was halting food aid to hundreds of thousands of North Koreans because of an unprecedented slump in donations.
The shortfall, coinciding with a political standoff between Washington and Pyongyang, had forced the WFP to cut supplies to people in the east of the isolated Communist nation after saying late last year it would halt aid to 2.9 million in the west.
"We continue to hear that our food is being diverted to the military," Hall said, saying the reports came from individuals and non-governmental organisations.
"We don't like that. The food is not designed for that. The food is aimed especially at women and children people who are hurting."
Hall said the United States was working through the Rome-based WFP as it negotiated in North Korea for a much more thorough monitoring of food aid handouts.
"We haven't heard what the results of those talks are yet. But we are pressing, and we are very concerned about it."
WFP executive director James Morris last December said donors were concerned because the North Korean authorities had not handed over a full list of those receiving the food aid and had restricted access to hunger zones.
He said the WFP had access to only 162 of the 206 counties in North Korea.
The United States has been the biggest donor of food to North Korea, providing 68% of contributions to WFP operations in North Korea in 2002, according to US figures.
In cash terms, US contributions to WFP operations in North Korea dropped to $63 million in 2002 from $102 million in 2001 and $185 million in 2000.
The US has not yet announced a pledge for 2003. The European Union has pledged $10 million for this year, and Italy has pledged a further $3 million in bilateral aid.