Mr Clinton: Confront the challenge

"When we get the Pope and the pop stars all singing on the same sheet of music, our voices do carry to the heavens," he said.

Mr Clinton said that Bono's "passionate devotion" had brought together politicians of different persuations.

"Global poverty is a moral affront, and confronting the challenge is simply the right thing to do," he told the audience at a White House ceremony.

Bono has been involved with causes to help impoverished nations since the days of Band Aid and Live Aid.

In the past two years he has met the Pope and the head of the World Bank, James Wolfenshohn, as part of his work for debt relief pressure group Jubilee 2000.

The legislation signed by Mr Clinton is part of an international plan endorsed by the G7 group of nations last year.

It aims to wipe out $90bn of debt owed by the world's poorest nations, reducing the total to about $37bn.

The relief is given on the condition that the savings are used on projects such as education and healthcare, and the recipients do not engage in military conflict.