Bono has praised Pope John Paul II "best frontman" the Roman Catholic Church ever had.
The Irish singer - who once famously gave the Pope his trademark wrap-around sunglasses to wear during a meeting, dubbing him "the first funky Pontiff".
He joined millions of people around the world mourning the Pope's death on Saturday.
The pair met in 1999 to push for rich nations to write off third world debt as part of a continuing campaign which has seen both men nominated for this year's Nobel Peace Prize.
In a statement released yesterday, Bono said: "A great show man, a great communicator of ideas even if you didn't agree with all of them, a great friend to the world's poor which is how I got to meet him.
"Without John Paul II its hard to imagine the Drop The Debt campaign succeeding as it did."
The late Pope, a fan of popular culture, once invited Bob Dylan to perform for him at a church congress in Bologna and joined the Eurythmics, Alanis Morissette and Lou Reed at a concert in Rome, Italy in aid of debt reduction.