The contentious issues include the Serbs' refusal to open a civilian crossing into Sarajevo and imposition of new restrictions on the movement of UN staff, and the government's failure to withdraw from a demilitarised zone (DMZ) west of Sarajevo.
In the UN "safe area"of Bihac, Bosnian troops retook several miles of land in an offensive on Friday night. The Serbs then shelled Bihac at the weekend, killing seven civilians.
The town remained tense yesterday, but relatively quiet. Military observers counted 20 explosions around the town yesterday. But a UN official in Bihac, Ed Joseph, warned: "Clearly, it's an unstable situation. I don't think there has been any sea-change stabilising event."
In Sarajevo, UN officials are seeking talks between Hasan Muratovic, a government minister, and Momcilo Krajisnik, speaker of the Bosnian Serb assembly in Pale, to resolve the impasse over the DMZ and the airport roads.
"Until we see political candour and acceptance of the ceasefire by both parties, the entire process will be under threat," Paul Risley, a UN spokesman, said.
The "blue routes" across Sarajevo airport, neutral ground controlled by the UN, connect the capital to government-held central Bosnia and the Croatian coast, and link two Serb-held suburbs. The Serb leadership in Pale reneged on a deal to open the roads because they want food convoy access restricted to eight UN-approved organisations already entitled to enter Sarajevo. The government wants passage for commercial convoys restored.
"What the Bosnian Serbs are offering actually falls far short of the promised freedom of movement across the airport routes," said Kris Janowski, a spokesman for the UN High Commissioner for Refugees. "It's quite clear the Serbs have no intention of allowing normal traffic into Sarajevo so the city can revive. They want to maintain an effective siege."
A helicopter inspection of the DMZ beyond the airport yesterday found Bosnian troops in the area. Their deployment is of no military significance but breaches the new year's eve agreement, UN officials said.
"It's not going to hurt the Serbs' position one iota to let a couple of buses full of elderly civilians cross, but they won't move," Mr Risley said. "Neither of the parties sees a benefit in being the first to budge on either of these issues, neither of
which means very much." Apart from the lull in fighting, he said, "We have nothing we can clearly point to as specific progress. But it would just take a `yes' and we'd have something."Reuse content