BUENOS AIRES (AFP)--The presidents of Argentina, Brazil and Venezuela are to hold an impromptu summit late Monday in Buenos Aires, Argentina's state news agency Telam reported.

The reason for the unscheduled get-together of Cristina Kirchner of Argentina, Luiz Inacio Lula da Silva of Brazil and Hugo Chavez of Venezuela was not given.

While Lula's visit to Buenos Aires was scheduled - he arrived Sunday with Brazilian officials and business chiefs and was to lunch with Kirchner Monday - Chavez's presence was a surprise.

Telam said Kirchner and Chavez were to fly together to Bolivia on Tuesday to also hold talks with that country's president, Evo Morales, in the southern town of Tarija.