Palitha Kohona, the head of Colombo's peace secretariat, said the Tigers were trying to stay away from the talks rescheduled for April 24-25.
They were originally due to start on April 19, but pushed back after the rebels asked for more time.
"I believe the ball is now in their court," Kohona told AFP.
"We are doing everything to go to Geneva for the talks but we can't clap with one hand. There must be commitment by both sides."
For their part, the Tigers accused the navy of scuttling preparations for the talks by "excessive interference" in the transport of rebel field commanders between the east and the north of the island on Saturday.
The Tigers had said they wanted internal consultations among field commanders before the Swiss talks but the navy had imposed condition