Colombian President Alvaro Uribe last night halted efforts by Venezuelan leader Hugo Chavez to mediate the release of hostages held by left-wing Farc rebels.
Mr Chavez had been invited by Colombia in August to broker a deal in which rebel kidnap victims, including French-Colombian politician Ingrid Betancourt, would be exchanged for militants held in government jails.
The Venezuelan president spoke with a Colombian armed services commander and requested information about the hostages, according to a statement from Mr Uribe.
That violated an agreement that only Mr Uribe and Mr Chavez would hold discussions between the two neighbouring countries about hostages held by the Revolutionary Armed Forces of Colombia, or Farc, the statement said.
Mr Uribe had said Mr Chavez may be the only person who could obtain the release of the hostages because the Farc rebels respect the left-wing leader.
Farc are holding dozens of high-profile hostages including police officers, former members of Congress and provincial governors.
Ms Betancourt was taken during her 2002 presidential campaign, and three Americans were captured after their plane crashed during a 2003 anti-drug mission.