Samaritan's Purse, one of five US groups that visited the impoverished communist state in February, said that a harsh winter killed crops and some North Koreans were already eating grass, leaves and tree bark.
‘We believe that, in many of the areas that we visited, in mid-June they're going to run out of food,’ said Ken Isaacs, the Christian-oriented group's vice president for programs and government relations.
Isaacs said that the relief groups want to provide 160,000 to 175,000 tons of food to North Korea -- about half of what the regime requested -- but that it would be impossible to arrange shipments in time to meet the shortfall.
‘If a green light was given today, that food probably isn't going to be into North Korea for about three months,’ Isaacs told a seminar at the American Enterprise Institute think-tank.
His warning came as former US president Jimmy Carter, a proponent of engagement with North Korea, led a delegation of elder statesmen to Pyongyang for talks on issues including food aid.
But US President Barack Obama's administration has held off on deciding whether to provide food assistance, with officials saying they want more evidence of an urgent need before committing to assistance.
Several lawmakers from the rival Republican Party have urged Obama not to authorize aid, suspecting that North Korea wants the food for its elite or to stock up for next year's celebrations marking the 100th birth anniversary of the regime's founder Kim Il-Sung.
Hundreds of thousands of North Koreans died in a famine in the 1990s. But North Korea, which prides itself on its ‘juche’ philosophy of self-reliance, abruptly kicked out the US aid groups in 2009.