Bosnia's top international envoy Paddy Ashdown has denied accusations that he acted unconstitutionally by sacking nine Bosnian Serb officials.
Ashdown says the officials were shielding war crimes suspects
The sackings have led to the prime minister and foreign minister resigning in protest.
Mr Ashdown said his job was to protect the 1995 Dayton peace accord that ended conflict in Bosnia.
He said the officials had obstructed attempts to bring war crimes suspects to justice - a cornerstone of Dayton.
"Most people will recognise it would be illegal for me to do things that were unconstitutional or contrary to the Dayton agreement," he told the BBC in response to claims that his actions had flouted the constitution.
Mr Ashdown dismissed six policemen and three others on Thursday accused of impeding the hunt for suspects.
He said he had no choice. "To act contrary to the Dayton agreement, upon which the peace of Bosnia-Hercegovina is based, will require action.
"My job is to protect Dayton and I had no alternative but to take the action that I took."
As the International High Representative in Bosnia, Mr Ashdown has sweeping powers that date back to Dayton.
But the Bosnian Serb Prime Minister, Dragan Mikerevic, resigned in protest saying: "I am not prepared to accept the threats and ultimatums."
He was followed on Saturday by his Foreign Minister, Mladen
The US has also announced sanctions against Bosnian Serb politicians, comprising a visa ban and a freeze of a leading political party's assets.
UN lawyers accuse Bosnian Serb leaders of shielding war crimes suspects.
Since the establishment of the international war crimes court in The Hague, the Bosnian Serb republic has not arrested a single suspect believed to be hiding on its territory.
At the top of the court's list of suspects are Radovan Karadzic and Ratko Mladic, leaders wanted for the campaign of "ethnic cleansing" that swept Bosnia during the war in the 1990s.