Serbia is to get a Western-leaning government after the Socialists opted on Monday to join a pro-European Union alliance headed by President Boris Tadic's Democratic Party.

Their decision ended six weeks of tense negotiations following an election which would have given nationalist, anti-EU parties the opportunity to form a government had they clinched Socialist support.

The news will come as a relief to Western capitals keen to see Serbia take its place firmly in the European mainstream after the wars in the Balkans in the 1990s.

"A majority of the party executive backed the formation of a government with the pro-European alliance," Serbia's state news agency Tanjug quoted Socialist leader Ivica Dacic as saying.

Details on the final division of cabinet roles are expected to be agreed by the end of the month.

Western worries about Serbia's future intensified after the May 11 election in which the Democrats emerged as the largest party but did not get a majority in the 250-seat parliament.

The nationalist Radicals and the DSS of outgoing Prime Minister Vojislav Kostunica came second and third and joined forces, brought together by their virulent opposition to EU membership until the bloc stops backing Kosovo's independence.

The Albanian majority in the former southern province, Serbia's medieval heartland, declared independence in February with the EU's blessing.

The nationalists tried to woo the Socialists by focusing on their common stance on issues such as Kosovo, and reminding them of their legacy as a party founded by the late nationalist leader Slobodan Milosevic.

But they underestimated the Socialists' desire for rehabilitation after having been blamed for the wars, isolation and poverty caused by Milosevic's policies in the 1990s.

The party eventually refused to freeze Serbia's EU bid, arguing that the economic progress it could offer was key to the generous social policy they promised their voters.

FRESH START

"I know this decision will not be understood by part of our electorate," Dacic said on Monday, "but this is a big comeback for the Socialists and an opportunity for a new start."

The Democrats have not yet commented on Dacic's announcement but had already made clear they were ready to seal a coalition with the Socialists in a spirit of national reconciliation.

Once critics of Milosevic's nationalism, the Democrats now say they will help the Socialists rebrand and could dilute economic reforms to accommodate their partner's populist agenda.

Sources say Socialist officials stand to get several powerful ministries and lucrative positions in Serbia's many state firms.

The EU has indicated it will reward Serbia by accelerating its progress towards EU membership. That could deliver tangible financial benefits and bolster the new government's chances of lasting a full term.

But some EU members remain adamant that short-term sweeteners aside, Serbia must not be allowed to join the bloc until it has fully faced up to its role in the Yugoslav wars by arresting war crimes fugitives.

Former Bosnian Serb army commander Ratko Mladic, Bosnian Serb political leader Radovan Karadzic and Croatian Serb wartime leader Goran Hadzic are still on the run and are believed to be hiding in Serbia or in the Serb-run half of Bosnia.