Irish rocker Bono met with U.S. Defense Secretary Robert Gates on Tuesday in his efforts to persuade world leaders to increase aid to developing nations.

The U2 frontman and humanitarian has already pressed French president Nicolas Sarkozy to stick to plans to raise development assistance to poorer countries, particularly those in Africa, and he continued his campaign with a low-key meeting at the Pentagon in Washington, D.C. this week.

Press secretary Geoff Morrell confirmed the 20-minute chat had taken place, saying: "They discussed… their shared desire for greater civilian participation in tackling the problems afflicting that region."