The ruling coalition of his party and that of Premier Vojislav Kostunica fell apart. With an eye to Serbia to joining the European Union, Tadic claimed the disagreement over Kosovo's independence would further isolate Serbia.

Kostunica, however, said the EU must acknowledge the illegitimacy of Kosovo before Serbia enters into talks over membership, a correspondent for Russia's Novosti news agency reported.

The predominantly Albanian leaders of Kosovo declared independence on Feb. 17, and 18 of the European Union's members have officially recognized the new country.

Kostunica issued a statement Tuesday saying the coming federal election would give Serbs a chance to show the EU the national resolve to maintain Kosovo as part of the country.

It was widely expected the parliamentary elections would be scheduled May 11, as local and provincial elections are already taking place that day, the Beta news agency said.