The government said on Friday talks were due to start in Switzerland on 15 February and were necessary to stop recent violence from escalating and reviving a two-decade-old war.
The Liberation Tigers of Tamil Eelam (LTTE) demand that any talks should focus on implementation of a ceasefire agreed in 2002, and, in particular, a clause that stipulates that the state must disarm paramilitaries the rebels say are attacking them. They also warn that talks are doomed if the government tries to amend the terms.
An anonymous rebel source said: "15 February is completely out. The Tigers are keen to go to Geneva for talks; but the Tamils Rehabilitation Organisation (TRO) abductions have affected the atmosphere."
"The Tamil people are in a panic and are very upset, so the Tigers cannot meet the government's 15 February talks deadline, and are instead aiming for talks at the end of February," he added, referring to the reported abduction of 10 TRO aid workers that some officials fear is a Tiger propaganda stunt.
The rebels say the 10 were abducted by government-backed paramilitiaries in the island's east. The claim has been denied by the government and the military.
Three have since been released, but details of the reported abductions remain vague.
The LTTE wants the government to disarm paramilitaries from a renegade rebel faction led by a breakaway commander called Karuna, who many officials suspect are behind a series of attacks in territory in the north and east controlled by the mainstream group.
Government officials were not immediately available for comment on the LTTE decision. The government has refused to do so to date, but has ordered an inquiry into the fate of the seven aid workers still missing.
Solution long way off
Diplomats and analysts fear that Sri Lanka could slide back to war unless the two sides follow through on the Geneva talks plan and start to build long absent trust.
But even if the government and the rebels finally agree on a date for talks after weeks of wrangling over where to hold them, peace envoys say that any lasting solution is still a long way off.
New president Rajapakse (R) has
been unexpectedly moderate
New President Mahinda Rajapakse has already flatly ruled out the LTTE's demands for a separate homeland in the north and east for ethnic Tamils, and some analysts fear the rebels are insincere about peace in the first place and have simply used the truce to buy time to regroup and rearm.
Rajapakse, who came to power after the Tigers ruined the November presidential election chances of the candidate seen best placed to reach a peace deal by scaring voters away with a boycott, has proved to be more moderate than many had expected.
He called for national unity during a national Independence Day address on Saturday, but parades of rocket launchers and tanks in the capital sent a strong visual message to the Tigers.