The leader of the Democratic Party of Serbia, Vojislav Kostunica, said he did not support the idea of introducing a transitional government, the main demand of the rally.

Mr Kostunica's decision follows a similar move by the opposition Social Democracy Party, led by Vuk Obradovic, which has called for the rally to be cancelled.

It said the opposition's first objective should be Mr Milosevic's resignation.

The rally has been organised by an independent group of economists, called G-17, to support the formation of a transitional government, which would foster economic recovery and re-establish ties with the rest of the world.

But Mr Kostunica complained such a government would have little influence over the Serbian parliament, which is currently dominated by Mr Milosevic's Socialist Party of Serbia and the ultra-nationalist Serbian Radical Party.

'A very strange group'

On Friday, Social Democratic Party leader Mr Obradovic said the rally was "weirdly organised by an even stranger group".

"We are against the rally being used as an opportunity to extend the agony with the regime personified by Slobodan Milosevic," added his brother and party Vice-president Pavic Obradovic.

Mr Draskovic is backing the rally

However, two main opposition leaders, Vuk Draskovic and Zoran Djindjic, of the Serbian Renewal Movement and Democratic Party, have said they will take part.

The Serb Orthodox Church, which opposition leaders consider a key element in their campaign against Mr Milosevic, will send a top official to address the crowd, according to rally organisers.

Protests continue

Plans for the rally follow a month of anti-government protests which have made three demands: Mr Milosevic's resignation, a transitional government, and free and fair elections.

Demonstrations continued on Saturday in Zajecar, eastern Serbia, where a protest calling for Mr Milosevic's resignation drew some 2,500 people.

The rally, held under the theme Serbia or Milosevic, was organised by the Alliance for Change, an opposition coalition dominated by Mr Djindjic's Democratic Party.