The Bosnian Serb leader, Radovan Karadzic, threatened to withdraw all offers of territorial concessions to Bosnian Muslims yesterday unless they accepted a peace deal by 15 January when talks are due to resume.
Mr Karadzic said the Bosnian Muslims did not want a settlement and the Bosnian Serbs could not go on waiting while the Muslims made what he termed ever-increasing demands for Serbs to hand over land.
Bosnian Serb and Croat forces have halted aid convoys to more than 1.5 million people trapped by war in Sarajevo, central Bosnia, eastern Bosnia and Bihac, a spokeswoman for the United Nations High Commissioner for Refugees said yesterday.
UN relief officials said pilots would fly food and medicines into Sarajevo on Christmas Day because Serbian forces had effectively cut the city's land links with the outside world.
During hours of artillery and mortar battles between the Serbs and Bosnia's Muslim-led forces, scores of shells fell on Zuc, a government hilltop position on Sarajevo's outskirts. In central Bosnia, where 68 people were reported killed in Muslim- Croat clashes on Wednesday, sporadic fighting continued and the Muslims consolidated advances in the Croat-held Lasva valley.
The Muslims, Serbs and Croats agreed in Brussels on Wednesday to observe a ceasefire from today until 15 January, but failed during a second day of talks yesterday to make progress on an overall settlement. 'On the political situation, there are no agreements,' Lord Owen, the international mediator, said.
Spain's Foreign Minister, Javier Solana, said some warring parties believed, mistakenly that they could gain military advantages by the spring if they carried on fighting.
The Bosnian Croat leader, Mate Boban, appeared to remove one obstacle to a settlement by agreeing to temporary European Union administration of Mostar, where Croats and Muslims are fighting for control. But Douglas Hogg, the Foreign Office minister, observed: 'Right at the end, Boban said 'yes' but in circumstances that made it quite clear he did not believe in it.'
The talks also covered the status of Sarajevo and the question of access to the Adriatic Sea for a future rump Bosnian Muslim state. The Bosnian Serbs are demanding the abandonment of plans to put Sarajevo under United Nations administration and are pushing instead for the partition of the city into Serbian and Muslim sectors. The Croats are opposed to a Muslim demand for access to the sea at the port of Neum.