DAKAR (AFP) -- The United Nations warned that west Africa this year will face biting food shortages over a longer-than-usual period, with Niger being the worst affected.

"After the food crisis that engulfed the region last year, this annual 'lean season' is starting earlier than usual in some of the world's poorest countries," said the World Food Organization (WFP) in a reference to the precarious months between the exhaustion of food stocks and new harvests.

"Many people are already feeling its bite despite what was generally a good harvest across the Sahel at the end of 2005," said the WFP statement released in Dakar. Africa's Sahel countries are located south of the Sahara desert.

"No country in the Sahel faces a more difficult lean season than Niger, where last year's crisis has left a deep scar, pushing thousands of the poorest further into poverty and debt," WFP said.

The lean season normally runs between April and October.

International donors have contributed only around 30 percent, or 16.5 million dollars, of the 54 million dollars that WFP is seeking to feed some 3.3 million people facing starvation in Mauritania, Mali, Niger and Burkina Faso.

The WFP regional head for west Africa, Mustapha Darboe, said every year has become a "crisis year" for the Sahel and "for too long this has been widely considered to be normal and acceptable.

"It is not. People should not be chronically short of their daily needs in the 21st century," he said.

"Last year's crisis in the region, especially in Niger, was a wake-up call to everyone; invisible hunger and unchecked poverty kill people," he added.

About 3.2 million people were hit by severe food shortages in Niger in 2005, although the government was slow to admit there was a problem.

By the end of last year Niger's Rural Development Minister Moussa Labo said nearly two million people would be affected by shortages in 2006.