OSLO (Reuters) - Peace negotiators for Colombia's government and Marxist rebels have not yet left for Norway, raising the chance talks could be further delayed and the sides would miss their only publicly scheduled event on Wednesday.

Government negotiators are still in Bogota, preparing to leave, a Colombian government source told Reuters, while Revolutionary Armed Forces of Colombia (FARC) rebels are in Cuba, resting up after their trip from the jungle, Colombian newspaper El Espectador said.

The parties have several times delayed the start of their talks aimed at ending a half a century of conflict, raising doubts they could physically be in Oslo for their event scheduled for Wednesday afternoon.

Norway's Foreign Ministry said the news conference was still scheduled but it would not release information about the exact time and place, saying it was up to the Colombian parties to finalize.

The two sides agreed in August to begin negotiations in Oslo in the first two weeks of October before moving on to Havana for the substantive part of their talks, the latest attempt after several failed attempts at peace.

FARC leaders earlier said that there had been logistical delays in getting Ivan Marquez, a member of the seven-member secretariat and FARC negotiator, to Cuba, and there were also delays in lifting international arrest warrants for some FARC delegates planning to go to Europe.

Colombian news reports have indicated a conflict about the composition of the FARC delegation, particularly the inclusion of Dutch national Tanja Nijmeijer.

In a statement dated October 15, FARC insisted it had the right to select team members and said Nijmeijer would be part of the delegation from October 21 to 27.

However, they did not make it clear if she would travel to Oslo or would only take part in the Cuban leg of talks.

A 10-year military offensive has weakened FARC but has been unable to end the conflict, leaving President Juan Manuel Santos vulnerable ahead of elections in 2014.

Negotiations in Oslo are expected to focus on laying the groundwork for later discussions and the parties would then focus mainly on land, drugs and political participation issues in Cuba.

Norway and Cuba have agreed to act as guarantors at the talks while Venezuela and Chile would "accompany" the talks.

(Reporting by Balazs Koranyi and Anna Valderrama; Editing by Alison Williams)