The findings, the result of a needs assessment conducted in February and March, will add to pressure for the United States to resume food aid to North Korea suspended in 2009 after its monitors were expelled. But doing so could be seen as aiding a government that has since advanced its nuclear weapons programs and is accused of twice attacking U.S. ally South Korea.
In its report, the result of an assessment conducted in February and March, the U.N. said that North Korea has suffered a series of shocks including summer floods and then a harsh winter, "leaving the country highly vulnerable to a food crisis."
It said the worst affected include children, women and the elderly, and recommended providing 430,000 metric tons (475,000 tons) of food aid.
North Korea's public distribution system will run out of food at the beginning of the "lean season" that runs between May and July, between spring and fall harvests. This would "substantially increase the risk of malnutrition and other diseases," the report said.
An outbreak of the livestock disease foot and mouth detected in December also posed a "serious threat to food security," it said.
Three U.N. agencies - the World Food Program, the Food and Agriculture Organization, and UNICEF - conducted the assessment at North Korea's request. They visited 40 counties in nine of the country's 11 provinces.
Five nongovernment U.S. aid agencies that visited the North last month reported severe food shortages and alarming malnutrition among children.
The U.N. said the current nutrition situation appears to be "relatively stable" but is liable to deteriorate in the "lean season."
"Children who are now mild to moderately malnourished can rapidly become severely malnourished and decrease their chance of survival or full development," the report said.
The United States said Thursday it is still considering whether to resume food aid to the North, which has had chronic problems in feeding its people since its assistance from the former Soviet Union ended. The country suffered famine in the mid-1990s in which at least hundreds of thousands are believed to have died.
State Department spokesman Mark Toner said the criteria for deciding whether to give such aid are "apolitical."
Senate Foreign Relations Committee Chairman John Kerry said Thursday the results of the U.N. assessment were "dire" and called for resumption of aid if it could be properly monitored.
"It is tempting to withhold food assistance until North Korea abandons its pursuit of nuclear weapons or adopts economic reforms. But the North demonstrated during the famine in the mid-to-late 1990s, in which an estimated 5-10 percent of ordinary North Koreans died, that it is willing to allow its people to suffer enormously," the Massachusetts Democrat said in a statement.
International donors will be concerned that any food aid not be redirected from civilians to North Korea's powerful military. They will also seek to act in concert with South Korea if assistance is restarted.
Tensions remain high on the Korean peninsula after two deadly, unprovoked military attacks on U.S. ally South Korea in the past year.
The North also recently revealed it had developed a new means of generating fissile material that might be used for a nuclear bomb. Talks on it disarming its nuclear programs have stalled for nearly two years.