Haven't been able to find a cite for this. It's listed as unsourced on Wikiquote, no real sources in a Google search, Google Books can only attribute it to a random quote collection book, and volume 106 of U.S. New & World Report attributes it to Yassir Arafat!
This is our monthly thread for collecting these little gems and pearls of wisdom, rationality-related quotes you've seen recently, or had stored in your quotesfile for ages, and which might be handy to link to in one of our discussions.