An agreement has been reached on giving Serbs, Muslims and Croats equal status in all parts of Bosnia.
The deal on changing the country's constitution was signed by some of the key parties, but Serb representatives expressed last-minute reservations about the deal, and it wasn't signed by Croat and Muslim nationalists.
But correspondents say their objections may be over-ridden by the main international representative in the country - Wolfgang Petritsch - who has the power to impose a solution.
Correspondents say when the deal is in place, it will represent the biggest change in Bosnia's political structures since the end of the war in 1995, bringing the two ethnic parts of Bosnia closer together.
From the newsroom of the BBC World Service