Any territorial exchanges would probably focus on Sarajevo and the future of the eastern Muslim enclaves.

Similarly threatened is the third eastern Bosnian enclave, Gorazde, with 60,000 more.

Women and children in the eastern enclaves might lie down in front of U.N. vehicles to keep them from moving out.

If they continue to close down the convoys to the eastern enclaves, we may have to push them through by force.

Once the siege is broken, they will have to withdraw to their eastern enclaves.

One contact group official said today: "The eastern enclaves were always just bargaining chips for Sarajevo, though we could never say so.

Mr. Izetbegovic needs the pressure to give up the eastern enclaves.

"Clearly with respect to the protection of this particular eastern enclave, it has not been a good day."

The eastern enclaves and Sarajevo would be acutely vulnerable.

This, he added, would also allow the small eastern Muslim enclave of Srebrenica to obtain electricity.