Aid groups say Zimbabwe's decision to suspend the work of non-governmental aid organizations will affect up to several million people who are at risk of starvation, homelessness and disease.
The U.N. Undersecretary-General for Humanitarian Affairs, John Holmes, called the suspension "deplorable" and said children will be particularly affected.
The U.N.'s children's fund, UNICEF, said any action preventing children from receiving aid is a violation of child rights.
The aid group CARE said the suspension of all aid groups in Zimbabwe will have a disastrous affect on the country.
U.S. officials say the government of President Robert Mugabe is apparently trying to make itself the sole distributor of food aid in Zimbabwe, so it can use food as a political weapon.
Zimbabwe suspended the work of the aid groups on Thursday, accusing them of supporting the political opposition.
The agencies, which assist millions of Zimbabweans every month, deny the charge.
Speaking to reporters in Washington by video conference, the U.S. ambassador to Zimbabwe, James McGee said members of the opposition Movement for Democratic Change are being forced to surrender their identity cards, which are needed to vote, in order to receive food aid.
The E.U.'s humanitarian aid commissioner, Louis Michel, said he is deeply distressed at the thought of needy Zimbabweans losing aid.
The U.N. human rights spokesman, Rupert Coleville, told VOA that the Mugabe government's action is a "complete perversion of democracy."
Zimbabwe suffers from food shortages and an inflation rate of more than 160,000 percent.
Some information for this report privded by AP, Reuters and AFP.