The government and foreign aid agencies are unable to import enough aid stocks to feed almost half of the 14 million population that is estimated will eventually need assistance.
WFP said there was a rise in hunger-related diseases, children were dropping out of school and families were resorting to desperate measures such as surviving on wild fruit to cope.
President Robert Mugabe's government denies that its controversial land reform programme is exacerbating problems caused by the drought.
The government has been repeatedly accused of diverting food aid to its own supporters and ignoring opposition activists.
A United States official even warned that the US may have to take "intrusive" measures to ensure that food aid was properly distributed.
Shortfall
The WFP said it faces a food shortfall of close to 200,000 tonnes in Zimbabwe between now and March 2003.
It added that Zimbabwe's state-run Grain Marketing Board (GMB), which has a monopoly on distributing food, is being severely limited in its ability to import enough cereal due to an acute foreign exchange shortage.
The WFP says its food distribution operations have proceeded relatively unimpeded, despite repeated reports of government interference preventing food from reaching its political opponents.
The WFP and its partners distributed 20,000 tonnes of food to two million Zimbabweans in October.
"We are approaching the very worst period of the crisis, when 6.7 million Zimbabweans will need food aid and yet WFP does not even have the resources to meet our target of three million beneficiaries in November," it said.
"It is an extremely serious situation and it is only going to get worse," said Kevin Farrell, WFP representative in Zimbabwe.
"We will all have to work non-stop over the coming months if we are to prevent millions of people from starving in Zimbabwe."
He said that donors needed to do everything possible to increase the flow of food into the country, "otherwise the suffering that we are already seeing is only going to become more widespread and more acute".