Serbia's main opposition parties have joined forces in their struggle to remove President Slobodan Milosevic.

After a six-hour meeting on Monday, all but one of the 15 parties signed the joint strategy.

"We wanted to show the regime and the world that the opposition can unite," said Vladan Batic, a co-ordinator of the Alliance for Change group.

The parties agreed to start anti-government demonstrations in March if the authorities did not call early elections on all levels.

The BBC's Jacky Rowland says a high turnout at the demonstrations could represent a serious challenge to the government.

Breakthough

The agreement represents the highest degree of unity reached by the often-fragmented opposition this year.

Until now, opposition groups have been prevented from joining forces by the personal and political rivalry between Vuk Draskovic, leader of Serbia's largest opposition party, the Serbian Renewal Movement (SPO), and Alliance leader Zoran Djindjic.

Vuk Draskovic said everyone was "satisfied" with the outcome.

Only Momcilo Perisic, a former general and ex-head of the Yugoslav army, refused to sign the document, reportedly because it did not demand the resignation of President Milosevic.

Early elections

The opposition, including the SPO for the first time, will start a nation-wide campaign of street protests from 9 March if its demand for early elections is not met.

It has called on the Serbian Government to schedule nation-wide elections by the end of April.

Local elections are currently due in the second half of 2000, national elections in September 2001 and a presidential ballot in December 2002.

Recent opinion polls in Serbia have indicated that a united opposition would win the elections.

In a sign that they are getting worried, the authorities have unleashed fresh accusations aimed at undermining Mr Draskovic, who they claim is a traitor because of his links with the United States and its allies.

They also accuse him of contacts with the French secret service - allegations he vigorously denies.

Strategy for rehabilitation

The opposition document also outlines a strategy for rehabilitating Serbia in the international community.

In a letter to leaders of the US, EU, Russia and China, it demands an urgent end to the ban on international air traffic and oil trade.

The letter also called for all remaining international sanctions to be lifted once President Milosevic agrees to their election demands.

Further requests are for Serbia to be readmitted to the European security organisation, the OSCE, and a partial return of Yugoslav troops to Kosovo.