PEACE co ordinator, Mr Carl Bildt, said yesterday UN sanctions might be needed to persuade the Muslim, Serb and Croat nationalists, who won Bosnia's elections, into sharing power.
"We need to beef up the structures of civilian implementation of the Dayton accords and we are having a dialogue on that," Mr Bildt said.
"Will there be some sort of sanctions instrument given by the Security Council for the next few years? I don't know. But I would certainly be in favour of that, a wider or more graduated sanctions instrument," he said.
Candidates of the Moslem Party of Democratic Action (SDA), Serb Democratic Party (SDS) and Croatian Democratic Union (HDZ) took the three seats on a new collective presidency.
The parties have also built up unbeatable margins to dominate a new Bosnia wide parliament and two regional assemblies, according to near complete returns released yesterday.
Mr Alija Izetbegovic's SDA was polling 54.3 per cent of the vote for two thirds of the 42 seats in the Bosnian House of Representatives.
The Croat HDZ tallied 23.4 per cent.
In the race for seats allotted to parties running in the Serb Republic, the ultra nationalist SDS won 54.3 per cent.
The presidency of the Bosnian Serb republic was secured by Mr Biljana Plavsic, SDS, with 65.1 per cent.
Under Dayton, the national presidency is to govern by consensus while quorum majorities will suffice in the assemblies. But legislation can be blocked by an faction perceiving "a threat to the vital interests of its people".
Mr Bildt said he had extracted pledges of co operation in earlier talks with presidency members.
Mr Bildt's team has its work cut out for it in coming weeks.
Once the elections are certified, expected to happen by September 25th, the presidency must convene for the first time to start appointing a cabinet. But Muslims and Serbs are already at heads over where to meet.
Meanwhile, NATO Secretary General Javier Solana said yesterday the alliance would have to remain engaged in Bosnia beyond the end of this year.