Zimbabwe ? A U.S. diplomat criticized the Zimbabwe government Saturday for interfering with aid efforts and warned of outrage in Congress over the worsening humanitarian crisis.

Tony Hall, the U.S. ambassador to the U.N. World Food Program and Food and Agriculture Organization, said the United States would donate $51.8 million worth of food for Zimbabwe and the neighboring drought-stricken countries of Zambia, Malawi, Lesotho and Swaziland.

The 73,500 tons will be sufficient to feed 5 million to 6 million people for a month, he told reporters at Harare airport.

The World Food Program says up to a third of Zimbabwe’s 12 million people may suffer from food shortages.

Hall said Zimbabwean bureaucracy was keeping 10,000 tons of food aid from U.S. relief groups “bottled up” in the South African port of Durban, over alleged lack of import licenses.

An aid convoy from the South African Council of Churches has also been held up for nearly a week as officials insist on certificates to prove it contains no genetically modified food.