Bosnian Serb PM Milorad Dodik favours greater autonomy
The parliament of the Bosnian Serb Republic - Republika Srpska - has passed a law making it easier to hold referenda on national issues.
It is being seen as a possible step towards an independence referendum.
Bosnian Serb PM Milorad Dodik objects to the presence of an international high representative, imposed under the Dayton Accords after the Bosnian War.
Mr Dodik says he intends to hold a vote gauging support for Dayton and decisions by the high representative.
The US and EU have warned that could destabilise Bosnia's constitution.
The Dayton peace accord of 1995, which ended Bosnia's devastating war, divided the country into two semi-autonomous entities: the Serb-dominated Republika Srpska and the Bosniak-Croat Federation of Bosnia-Hercegovina.
Overseeing it all was the high representative - the top international politician in the country.
The passing of the new law sets up Republika Srpska to directly challenge his authority and therefore Bosnia's state power, says the BBC's Balkans correspondent Mark Lowen.
That, warns the international community, could severely threaten Bosnia's sovereignty.
The real fear for the international community, though, is that Mr Dodik will eventually call a referendum on independence for Republika Srpska, our correspondent says.
He has frequently supported the idea in the past, although lately seems to have toned down his secessionist rhetoric.