Bosnian leaders should not miss an EU- and US-backed opportunity to reform the constitution and make the country function better, visiting British Foreign Secretary David Miliband said on Friday.

- These are important times when (Bosnian) leaders are going to be making important choices that will affect the European and NATO membership aspirations of their country - Miliband said following talks with Bosnian leaders.

The appeal came after Brussels- and Washington-backed talks between Bosnia's Muslim, Croat and Serb leaders at the EU peacekeepers' Butmir base near Sarajevo last month failed to end a long-standing deadlock on how the divided country should be governed.

- I very much hope that all the leaders will continue to engage positively with the Butmir process because I think that it offers a very important chance for Bosnia to make forward progress - Miliband said.

Since the 1992-1995 war Bosnia consists of two semi-independent entities -- the Serbs' Republika Srpska and the Muslim-Croat Federation -- linked by weak central institutions whose decisions must be backed by all three communities.

Reform of the Bosnian constitution has been demanded by the international community for several years. The Bosnian Serbs, however, have refused any modifications which might reduce their hold on power.

Despite the lack of progress at Butmir, EU and US technical experts have since been holding talks with Bosnian political leaders in the hope of winning their acceptance of the reform package.

- I have been at pains to stress to your leaders our concern to ensure that Bosnia will not fall behind other countries in the Western Balkans - Miliband said.

Despite recent intense diplomatic activity, Bosnian leaders appear to be determined not to accept the reform package which Croats and Muslims describe as insufficient and Serbs as going too far.

The package also includes proposals on how to fulfil conditions for closure of the powerful international envoy's office in Bosnia.

The fate of the Office of the High Representative, established to oversee the peace process under the deal that ended the war, will be discussed at a meeting of the 55-nation Peace Implementation Council in Sarajevo on November 18.

The council oversees post-war Bosnia and the work of the High Representative who has the power to impose laws and sack obstructive elected officials.

Unlike his Russian counterpart Sergei Lavrov who said during a visit to Sarajevo on Thursday that his country will push for a prompt closure of the OHR, Miliband said that there was "significant conditionality" attached to that happening.

- We support that conditionality. It was entered into for serious reasons and it needs to be taken seriously - Miliband said.

- All the difficulties in achieving the conditions explain the support in the EU and in the US for the Butmir process - he added.

Since the end of the war, Bosnia has comprised of two entities -- the Serb-run Republika Srpska and the Muslim-Croat Federation -- linked by weak central institutions and with their own president and government.

Reform of the Bosnian constitution has been demanded by the international community for several years.