By Hugh Bronstein

BOGOTA (Reuters) - Latin America's one-time 'odd couple' is in no mood for hugging.

A simmering dispute between Hugo Chavez and Alvaro Uribe, the hard-willed, politically opposed presidents of Venezuela and Colombia, has exploded into diplomatic dog-fight that threatens to destabilize the region.

The crisis erupted after Colombian forces entered Ecuador on Saturday to kill a Colombian rebel leader.

Uribe charges leftist allies Ecuador and Venezuela with supporting the guerrillas; Chavez and Ecuadorean President Rafael Correa have cut diplomatic ties with Colombia and sent troops to their neighbour's border, vowing to meet any future incursions with force.

The military and diplomatic hostilities have blown away a once-chummy relationship between fiery leftist Chavez and the conservative, studious-looking Uribe.

For years they appeared to get along so well they were dubbed the odd couple of Latin American politics. They were seen hugging and chatting amiably at public events as they seemed to set aside ideological differences, focus on trade ties and bond on common personality traits.

Chavez, who first won office in 1998, and Uribe, in power since 2002, both enjoy high popularity at home, like to micromanage government affairs and are given to folksy town hall-style speeches. Each has clinched constitutional permission to run for extra time in office.

But tension simmered under the surface as Uribe confirmed his place as Washington's chief ally in South America and former coup-leader Chavez, loved by many poor Venezuelans for his generous oil-export-funded social programs, called for region-wide revolution.