Colombian authorities on Sunday rejected charges from Venezuela that their troops had crossed the frontier in the latest incident to test fraying relations between the Andean neighbours.
Venezuela over the weekend accused 60 Colombian soldiers of entering its territory in what Caracas said was a provocation that aimed to destabilize the region.
The tension exacerbates sharp divisions in the Andes, where Colombian President Alvaro Uribe is a close Washington ally and Venezuela's Hugo Chavez a purveyor of anti-U.S. sentiment.
"There has been no incursion," Colombian Defense Minister Juan Manuel Santos told local radio, saying a river in the area would have prevented troops crossing. "It would have been practically impossible for it to happen as they say."
Tension has simmered since Colombia raided inside Ecuador and killed a rebel leader in March. After Ecuador broke off relations, Chavez ordered tanks to the porous border that cuts through jungle and mountains to support his leftist ally.
Venezuela said the incursion occurred on Friday, a day after Chavez said he would review diplomatic and trade ties with Colombia following an Interpol probe that helped reinforce charges that he supports Colombia's Marxist FARC guerrillas.
Colombian and U.S. officials say documents and files found on the captured computer of the slain rebel leader show that Chavez and Ecuadorean leader Rafael Correa have provided support to the rebels, who U.S. officials label cocaine-smuggling terrorists.
Chavez and Correa have dismissed these accusations as U.S.-inspired propaganda.
Despite occasional brinkmanship, fiery rhetoric and the risk of military missteps on the border, analysts say open conflict is highly unlikely. There is heavy cross-border trade among the three Andean countries.
Incidents along the Venezuelan and Colombia frontier are common as the rugged territory makes it hard to define exactly where the frontier is located in some spots.
Earlier this year a Venezuelan patrol got lost after crossing over in the north of the country. They were helped back into Venezuela by Colombian authorities.
