Serbia is holding run-off presidential elections Sunday, with voters having to choose between incumbent reformist Boris Tadic and nationalist Tomislav Nikolic.

The outcome of the vote may influence both Serbia's EU future and the future of the former province of Kosovo which declared independence in 2008, BBC analysts write.

Tadic, who has already served two terms in office, calls the vote a referendum on EU membership.

Nikolic, who has lost to Tadic twice, says he also supports the EU bid but not at any cost. In his campaign, he focused on the economy, promising fresh investment and higher tax on the wealthy.

Some analysts question the depth of the pro-European conversion of Nikolic, former right-hand man to Vojislav Seselj, now on trial for alleged war crimes in The Hague, in the nationalist Radical Party.

Even in the last elections in 2008, Nikolic ran against Tadic on a nationalist pro-Russian and anti-EU platform. But he and his followers later broke with the Radicals and formed the avowedly pro-EU Progressive party, taking many former Radical voters with them.

After the first round of the election on 6 May, the nationalist Progressive party accused Tadic's supporters of vote manipulation, a claim that was rejected both by electoral officials and foreign monitors.

In a presidential debate on Wednesday, Democratic Party leader, Tadic said: "We want a piece of that pie, conditions for jobs, guarantees for investments... Bosch, Siemens, Fiat, and Benetton would never have come to Serbia without the guarantee provided by the status of EU candidate."

Under his leadership Serbia carried out EU candidacy negotiations, and captured and handed to international prosecutors at The Hague Bosnian Serb war crimes suspects Radovan Karadzic and General Ratko Mladic.

During Wednesday's debate, Nikolic told Tadic: "Do not defend the EU against me because the EU does not defend itself against me.

Serbia has a staggering unemployment of 24% and foreign debt of EUR 24 B.