U2 frontman Bono continued his on-tour campaigning yesterday (01MAR06) by paying a visit to Argentine President NESTOR KIRCHNER, just two hours ahead of the band's Buenos Aires concert. The WITH OR WITHOUT YOU rocker made the surprise appearance at Government House Casa Rosada to discuss AIDS prevention and anti-poverty measures. The singer has already visited Chilean President RICADO LAGOS and Brazilian leader President LUIZ INACIO LULA DA SILVA during the band's 2006 Vertigo tour. U2 later performed at to a 50,000-strong crowd at the city's River Plate soccer stadium.