Cuba's President Fidel Castro, right, and Venezuela's President Hugo Chavez talks during a visit to the Ernesto "Che" Guevara museum in Alta Gracia

Cuban leader Fidel Castro and Venezuelan President Hugo Chavez led an anti-U.S. rally in Argentina following the end of a summit of the South American trading bloc, Mercosur.

Some 15,000 students and leftist activists gathered at the University of Cordoba late Friday to hear Mr. Castro and his close ally, Mr. Chavez, make speeches criticizing U.S.-backed policies they blame for many of the problems in Latin America.

Saturday, the two leaders traveled to the town of Alta Gracia to visit the boyhood home of Mr. Castro's late comrade, Argentine-born revolutionary Ernesto "Che" Guevara."

Guevara helped Mr. Castro lead his 1959 communist revolution in Cuba. Guevara was executed in Bolivia eight years later (in 1967) while trying to lead a socialist movement there.

The 79-year-old Mr. Castro, who turns 80 on August 13, made a rare international trip to appear at the Mercosur summit.

Mercosur members expanded a trade pact with communist-ruled Cuba, which has been under an economic embargo by the United States for more than four decades. The trading bloc also officially backed Venezuela's bid for a non-permanent seat on U.N. Security Council.

Argentina, Brazil, Paraguay and Uruguay formed Mercosur in 1991. Venezuela became a full member earlier this month. Chile and Bolivia are associate members.

Some information for this report was provided by AFP, AP and Reuters.