BRUSSELS, April 2 (Reuters) - U.S. aid to the world's poor fell 20 percent last year from 2005, while European Union aid rose, figures to be published by the OECD on Tuesday showed.

Rich countries' official aid to poor nations totalled $103.9 billion in 2006, down from $106.8 billion the year before, according to draft figures from the Organisation for Economic Cooperation and Development obtained by Reuters.

The United States was the single biggest donor in 2006 with $22.7 billion of aid, but that was down 20 percent from 2005 and represented 0.17 percent of its gross national income.

Aid from the EU's member states rose 2.7 percent to more than $59 billion, to which the bloc's executive Commission added some $10 billion. The total represented 0.42 percent of the bloc's gross national income, an EU official said.

The Paris-based OECD publishes aid figures from 22 rich countries and the European Commission every year.

Aid from those donors rose more than 30 percent in 2005 from 2004 because of large debt relief packages.