Izetbegovic had said on Friday night that he accepted the plan to end the 16-month war in the Balkan state, but he later sent peace mediators a letter saying he wanted guarantees that the 'union' would be a full state.
Under the plan, separate republics for Muslims, Serbs and Croats in Bosnia would be linked under a union presidency, council of ministers and parliament with limited powers on internal matters. But about 200 Muslim refugees gave Izetbegovic an emotional welcome outside the Geneva negotiating hall, urging him to preserve a united Bosnia.
Izetbegovic told mediators Lord Owen and Thorvald Stoltenberg that, while he was committed to negotiations, his experts believed the wording of the plan left doubts on the legal status of the new union.
His legal adviser, Professor Francis Boyle, from the University of Illinois, told reporters the accord as it stood was unacceptable because it called into question Bosnia's membership of the United Nations.
Boyle said a meeting with the mediators' legal expert, Paul Szasz, had confirmed this fear. He said that Szasz, an American who helped to draft Namibia's constitution on its independence, 'made plain that the purpose of the Owen-Stoltenberg plan is to divide the republic of Bosnia- Herzegovina into three independent states'. He added: 'Unless we have assurances from the Security Council and the General Assembly, our independent existence is jeopardised.'
Despite the row, Izetbegovic pressed on in negotiations with Serb leader Radovan Karadzic and Croat leader Mate Boban on a map determining the territory of each of the three republics.
Diplomats close to the talks said discussions were moving towards a division which would give about half of the country to the largely rural Serbs. The Muslims would get 29 per cent, including the major industrial centres they now hold, and the Croats 21 per cent. Before the war, Muslims made up 44 per cent of the population, Serbs 33 and Croats 17.
Lord Owen warned yesterday that elements in all three factions wanted to continue fighting. 'There are all sorts of people out there who want to continue the war, and will try to trigger incidents and try to derail the process. There are some very difficult issues that we have to resolve in the next day or so. Let's just hope and pray we can.'