The Colombian government has rejected a proposal by Venezuelan President Hugo Chavez to travel to Colombia to meet the leader of the Farc rebel group.
President Uribe (L) agreed a mediator role for Mr Chavez
Colombia's peace commissioner, Luis Carlos Restrepo, said the government did not consider the idea of a face-to-face meeting viable.
He repeated that Mr Chavez could meet the left-wing rebels in Venezuela.
Meanwhile, forensic experts said 11 Farc hostages - all politicians - had died of gunshot wounds.
The men died in disputed circumstances in June.
An international team examining the bodies said a report providing more details of the deaths would be presented to the secretary general of the Organisation of American States on Friday.
Their bodies were recovered at the weekend, and the authorities in Colombia have begun transferring their remains to their families.
Mr Chavez agreed last month to act as a mediator in negotiations between Farc representatives and the Colombian government.
On Sunday, Mr Chavez said he was "willing to go into the deepest part of the largest jungle to talk" with the Farc leader, Manuel Marulanda.
Mr Chavez also said he had received a letter from Marulanda, saying he was unable to travel to Venezuela, and invited the Venezuelan president to meet him in Colombia instead.
However, in a brief statement, Mr Restrepo said the government "does not consider appropriate" a meeting between Mr Chavez and the Farc on Colombian soil.
Among about 45 prominent hostages held by the rebels are three US defence contractors, whose small plane crashed in the jungle while on an anti-narcotics mission in 2003.
Also being held is former presidential candidate Ingrid Betancourt, a French-Colombian citizen.