The Organization of the American States, the region's top diplomatic body, will hold a crisis session in Washington on Tuesday to press for a negotiated end to a dispute that erupted after a weekend Colombia raid to kill a rebel inside Ecuador.

Ecuador's President Rafael Correa will also start a five-nation tour of the region -- including to leftist ally Venezuela -- to lobby for support against what he calls a premeditated violation of sovereignty.

"This is not a bilateral problem, it's a regional problem," Correa told Mexican television. "Should this set a precedent, Latin America will become another Middle East."

Latin American governments generally lined up to condemn conservative Colombian President Alvaro Uribe for sending troops and warplanes over the border in an attack on a jungle camp that killed a senior FARC rebel.

Nicaraguan President Daniel Ortega, a former guerrilla and a close leftist ally of Venezuela and Ecuador and who has a territorial dispute with Colombia, accused Uribe of becoming a threat to Latin America.

The region's diplomatic heavyweight, Brazil, demanded Uribe apologize to Correa. It also worked on the crisis with Argentina, whose president will visit Venezuela on Wednesday.

"This conflict ... is beginning to destabilize regional relations," said Marco Aurelio Garcia, Brazilian President Luiz Inacio Lula da Silva's foreign policy adviser. "We are mobilizing all of Brazil's diplomatic resources and those of other South American capitals to find a lasting solution."

U.N. Secretary-General Ban Ki-moon urged the three countries to exercise restraint and address their concerns "in the spirit of dialogue and cooperation that has traditionally characterised their relations," his spokeswoman said in a statement issued in Geneva just before he left for New York.

Major powers such as France and the United States, as well as U.S. presidential candidates, also urged diplomacy to defuse the tensions.

Venezuelan President Hugo Chavez, who has negotiated the release this year of rebel hostages, called the guerrilla leader's death a "cowardly assassination" by a U.S.-backed president who did not want more captives freed.

Chavez and Correa expelled Colombia's diplomats from their capitals on Monday.

Colombia also fuelled the tensions by accusing Chavez of funding Latin America's oldest insurgency -- a charge denied by the anti-U.S. president's aides.

Despite the three leaders' brinkmanship and the risk of military missteps, political analysts said a conflict was unlikely on borders that stretch from parched desert through Andean mountains and jungles to the Pacific Ocean.

Chavez, the leader of a growing bloc of Latin American leftist presidents, may fire up his supporters by challenging Uribe but he can ill afford to lose food imports from Colombia as he combats shortages in his OPEC nation, analysts said.