The Bush administration's cautious approach to Iraqi refugees offers little hope for those trapped in a growing humanitarian crisis that could begin to breed Islamist militancy if left unchecked, experts say.

The United States is the biggest aid donor to an estimated 4.2 million Iraqis driven from their homes.

But experts say assistance from the US and other Western nations is only a tiny fraction of what may be needed to stabilize the biggest Middle East refugee crisis since 1948.