Bosnia's international administrator will insist on implementing his plan to make the government run more efficiently, paving the way to the European Union.
Miroslav Lajcak, a Slovak diplomat who is the top international administrator in the ethnically divided country, rejected a Bosnian Serb request that "corrections" be made to the plan.
The proposal "is in force and is not negotiable," Lajcak's office said.
The developments raised the possibility that Bosnian Serbs will walk out of joint national institutions and block the functioning of the state.
The dispute revolves around Lajcak's proposal to change the way a quorum is calculated, so that parties cannot block reforms simply by not attending parliamentary sessions or cabinet meetings.
More broadly, it revolves around the degree to which the institutions of the country's two ethnically distinct mini-states will be merged. Bosnian Serbs, fearing the loss of their mini-state, the Serb Republic, have stayed away from meetings to block laws that may lead to the merger of government agencies.
Other parties have used the tactic as well. But the European Union is demanding that various institutions be merged as a prerequisite for membership.
Milorad Dodik, the leader of the Party of Independent Social Democrats, the most influential Bosnian Serb party, said his party would abstain from voting if Lajcak's plan was not changed - and two of his most important supporters would quit the government altogether.
"The leadership of the Parliament will be lost ... that's our answer to political violence," Dodik said.
Bosnian Prime Minister Nikola Spiric, a party member, resigned last week to protest Lajcak's plan.
Lajcak was holding firm, saying through his office that the Bosnian Serb proposal "does not constitute a basis for further discussions."
"Instead of streamlining and improving the decision-making process" in the government, the Bosnian Serb proposal "introduces new possibilities of blockage which did not even exist before," the statement said.
Bosnian Serbs, who control half of Bosnia, have hinted they may try to split the former Yugoslav republic in two if their internal autonomy is jeopardized.
The 1992-95 war in Bosnia, during which the Bosnian Serbs fought for unity with Serbia, left at least 100,000 people dead. The 1995 Dayton peace agreement ended the war but divided the country into two mini-states - the Serb Republic and a Bosnian-Croat Federation.