The United Nations is short of $2.5 billion of the $4.4 billion it needs this year to confront the world's worst humanitarian crises, the top U.N. aid official said on Tuesday.

U.N. emergency relief coordinator John Holmes said funding had reached 43 percent of the amount the United Nations had appealed for by the middle of 2007 -- a slight improvement on previous years.

But he said it was inadequate given the needs in places such as Sudan, Somalia and Palestinian territories.

"What we are talking about is really a few cents in the GDP (gross domestic product) of countries, the main donors, which are of course rich countries," Holmes told a news briefing after presenting a review to officials from donor countries.

The United Nations said in a statement that there were big disparities in funding and that it often bore no relation to the severity of a crisis. It said donors had given only 37 percent of the $687 million needed for the Democratic Republic of Congo.

Sixteen of the 19 severe humanitarian crises covered by the consolidated appeal launched last November 30 are in Africa.