Ecuadorean President Rafael Correa visited Latin American powerhouse Brazil on Wednesday on his regional tour to push Colombia to apologize for a military operation in Ecuador as an Andean crisis escalated.

Venezuela and Ecuador have moved troops to their borders and cut diplomatic ties with Colombia, which got backing from U.S. President George W. Bush on Tuesday, while diplomats in Europe and the Americas asked all sides for calm.

Many Latin American leaders have condemned Colombia for entering Ecuador to kill FARC guerrillas on Saturday.

The crisis has pitted Correa, Venezuela's anti-U.S. President Hugo Chavez and their allies in the left-leaning region against Colombia, which receives billions of dollars in U.S. military aid to fight drug traffickers and guerrillas.

"The aggressor has to apologize and the international community condemn him," Correa told journalists in Brasilia on Tuesday night. "If not we will have to defend ourselves with our own means."

Colombia said it has already apologized and said Correa should take responsibility for sheltering the rebels of the Revolutionary Armed Forces of Colombia, or FARC, the oldest insurgency in Latin America.

Chavez, who sent tanks to his country's border with Colombia, has warned war could break out, although political analysts say that is unlikely. Conservative Colombian President Alvaro Uribe accused Chavez of genocide for sponsoring the rebels, who Chavez is openly sympathetic to.

Correa was scheduled to meet with Brazilian President Luiz Inacio Lula da Silva on Wednesday before flying to Venezuela to meet with Chavez.

Argentine President Cristina Fernandez also was travelling to Caracas to meet with Chavez, who calls Bush "Mr. Danger".

Venezuela briefly blocked border trade with Colombia on Tuesday but political analysts said that measure was not sustainable since Venezuela depends on its neighbour for food supplies and prices could rise without Colombian imports.

Bush, who rarely refers to Chavez, weighed in on the crisis on Tuesday for the first time. He criticized Chavez's "regime" for "provocative manoeuvres" and said the superpower opposed any act of aggression that could destabilize the region.

Mexico joined Argentina, Brazil, Chile, Peru and others who condemned Colombia's violation of Ecuadorean sovereignty.

"We coincide in the rejection of any action that constitutes a violation of territorial sovereignty," Mexican President Felipe Calderon said after a meeting with Salvadoran President Tony Saca in San Salvador on Tuesday.

U.S. diplomats, meanwhile, worked to shift the focus to the FARC, which has killed or displaced thousands of people and kidnapped hundreds.

"We should not lose sight of the fact that it is the FARC, rather than any member state present here, that has undertaken repeated incursions and infringements of national sovereignty into the neighbours of Colombia," said Robert Manzanares, the U.S. ambassador to the Organization of American States, which held an emergency session on Tuesday.