Students of the Universidad Nacional protest against U.S. President George W. Bush's upcoming visit to Colombia, as riot policemen look on in Bogota March 7, 2007. *******/Jose Miguel Gomez (COLOMBIA)

A student of the Universidad Nacional gestures at riot policemen during a protest against U.S. President George W. Bush's upcoming visit to Colombia, in Bogota March 7, 2007. *******/Jose Miguel Gomez (COLOMBIA)

Demonstrators protest against the upcoming visit of US President George W. Bush to Colombia, in Cali, Colombia, Wednesday, March 7, 2007. President Bush will visit Colombia on March 11, 2007. (AP Photo/Diego Sinisterra)

Police officers fire tear gas to disperse a demonstration against the upcoming visit of US President George W. Bush to Colombia, in Bogota, Wednesday, March 7, 2007. President Bush will visit Colombia on March 11, 2007.(AP Photo/Inaldo Perez)

Demostrators throw stones and molotov cocktails to riot police during a protest against the upcoming visit of US President George W. Bush to Colombia, in Bogota, Wednesday, March 7, 2007. US President George W. Bush will visit Colombia March 11. (AP Photo/Inaldo Perez)

A demontrator throws a molotov cocktail at riot police during a protest against the upcoming visit of US President George W. Bush to Colombia, in Bogota, Wednesday, March 7, 2007. US President George W. Bush will visit Colombia March 11. (AP Photo/Inaldo Perez)

A student throws wooden sticks into a blaze during a protest against U.S. President George W. Bush's upcoming visit, in Cali March 7, 2007. Bush will visit Brazil, Uruguay, Colombia, Guatemala and Mexico on a week-long tour of Latin America. *******/Carlos Duran (COLOMBIA)

Students of the Universidad Nacional throw stones at riot policemen during a protest against U.S. President George W. Bush's upcoming visit to Colombia, in Bogota March 7, 2007. *******/Jose Miguel Gomez (COLOMBIA)

Anti-riot police fire tear gas during a protest by students of the Universidad Nacional against U.S. President George W. Bush's upcoming visit to Colombia, in Bogota March 7, 2007. *******/Jose Miguel Gomez (COLOMBIA)


Students burn a U.S. flag during a protest against U.S. President George W. Bush's upcoming visit, in Cali March 7, 2007. Bush begins a tour of Latin America countries that includes Brazil, Uruguay, Colombia, Guatemala and Mexico. *******/Carlos Duran (COLOMBIA)

Students burn a shirt with the U.S. flag on it during a protest against U.S. President George W. Bush's upcoming visit, in Cali March 7, 2007. Bush begins a tour of Latin America countries that includes Brazil, Uruguay, Colombia, Guatemala and Mexico. *******/Carlos Duran (COLOMBIA)

A Colombian student holds a banner with a picture of U.S. President Geroge W. Bush during a protest in Medellin March 7, 2007. Bush will visit Colombia on March 11. The banner reads: 'Wanted'. *******/Fredy Amariles (COLOMBIA)

People walk pass a graffiti against the upcoming visit US President George W. Bush to Colombia in Bogota, Wednesday, March 7, 2007. President Bush will visit the country on March 11, 2007. (AP Photo/Fernando Vergara)

Colombian riot police remove a motorcycle during a protest of university students in Cali, Colombia, Tuesday, March 6, 2007, against the next visit of U.S. President George W. Bush to Bogota. President Bush is expected to meet with Colombia's President Alvaro Uribe in Bogota next March 11, 2007. (AP Photo/ Inaldo Perez)

A Colombian student protests in front of a banner with pictures of U.S. President George W. Bush in Medellin March 7, 2007. Bush will visit Colombia on March 11. The banner reads: 'Wanted'. *******/Fredy Amariles (COLOMBIA)