There may have been a collective sigh of relief across the European Union at the news that Serbian President Boris Tadic had defeated his ultra-nationalist rival  in Sunday's election, but the optimism that Serbia will now firmly tread a pro-European path could be short lived.

Serbian Prime Minister Vojislav Kostunica, who had refused to endorse Tadic in the poll despite being in a coalition with his Democratic Party, is already threatening to scuttle a pre-membership deal  agreed with the EU last week.

The prime minister says the deal is a "hoax" designed to trick Serbia into approving the EU's proposed mission to Kosovo and recognizing the disputed province's independence. Last week Serbia had agreed to a deal with Brussels that would speed up Serbia's path to possible membership by boosting trade, political dialogue, visa liberalization and education.

The Serb infighting comes just a day after the EU formally agreed to send a police and civil administration mission to Kosovo, which has been under United Nations administration since the 1999 NATO bombing ended Slobodan Milosevic's ethnic cleansing campaign against Kosovo-Albanians. However, Brussels is still seeking the UN Security Council's formal blessing before finalizing the plans for the proposed 1,800-strong mission.

Kostunica, who opposes the EU mission, has explicitly linked Serbia's prospective EU membership with the Kosovo issue. In a statement released Tuesday, he said: "Signing the EU's proposal would be effectively signing to agree to Kosovo's independence." He has now called for a meeting of the Serbian parliament to reject the deal, which is scheduled to be signed on Thursday.

Tadic and his party, however, are insisting on signing. "After Tadic's victory, it is clear which course the Serb people have chosen to take, and that is toward the EU membership," Vice Prime Minister Bozidar Djelic, a member of the Democratic Party, said. But Investment Minister Velimir Ilic, a Kostunica ally in the ruling coalition, said that if the agreement is signed the cabinet could fall. "Thursday is D-Day," he told the Associated Press.

On Tuesday, German commentators express their cautious optimism after Tadic's victory, but many point out that he still has to convince many Serbs of the advantages of closer ties with Europe, while others insist that Serbia cooperate with the Hague Tribunal on war crimes before going ahead with membership talks. And many depict Kostunica as a stumbling block to the Serb turn to the West.

The Financial Times Deutschland writes:

"The result should not be a cause for euphoria. It is true that the issue of Europe interested a lot of Serbian voters. A narrow majority obviously is in favor of closer ties. But the Serbs' understanding of closer ties does not correspond to the EU's conception. There is little readiness to hand over the alleged Serbian war criminals to the Hague Tribunal. And Belgrade has shown little willingness to compromise in the conflict over Kosovo."

"The strong man in Serbia is not Tadic but rather Prime Minster Vojislav Kostunica, who has proven himself headstrong. The election is indeed a setback for the prime minister, who has tried to directly link cooperation with the EU and the Kosovo question. However, Kostunica has proven himself a crafty tactician in every situation."

"Kosovo should be accompanied to independence by a strong EU mission. And Serbia's path toward Europe should be made dependent on its cooperation on the war criminals issue. It is Tadic, the pro-European, who has the most to gain from this sort of consistent position."

The center-right Frankfurter Allgemeine Zeitung writes:

"Serbia not only needs an alternative to Radical Party leader Tomislav Nikolic's populist drivel but also to Kostunica's increasingly reactionary policies. The fact that Serbia's path toward Europe is blocked as long as he is prime minister should no longer be ignored."

"The majority of Serbs don’t want to just belong to Europe geographically. And they realize that the painful loss of a large part of Kosovo … has its roots in the era when Serbia had removed itself far from Europe in both word and deed."

"Behind all the rhetoric, the situation in southeast Europe should stabilize. Once the status question has been recognized as an established fact, Serbs and Kosovo Albanians will have the same goal for the first time in their history: to become members of the EU as quickly as possible."

"This alone will fence off the Serb-Albanian antagonism. Greater Serbia, Great Albania, as well as Greater Bulgaria, Greater Macedonia or Greater Croatia -- all of these ideas have been dreamed in the past and some have for a short while also been realized, always accompanied by the shedding of blood."

"The EU cannot conjure a new Balkans out of thin air. But it can provide a roof, under which these kinds of hegemonic and territorial fantasies lose both meaning and terror."

The conservative Die Welt writes:

"Serbian nationalists could still attempt to provoke unrest in the Serbian areas in Kosovo … but there is now far less danger of armed conflict."

"Despite the happy outcome, the presidential election showed that Serbian society is still split right down the middle between the nationalists, who still want to fight the battles of the past on the side of the Russians, and the moderate forces, who see Serbia's future in a united Europe. Therefore, the EU was right to offer the Serbs the prospects of entry in order to secure their 'good conduct' in the Kosovo question."

"It is also right that the overwhelming majority of EU states will recognize Kosovo's independence. The uncertain status has not only kept the Kosovo Albanians in limbo for years and prevented the province from developing, it has also been one of the main reasons for the fact that a large part of Serbian society has still not emerged from the time warp of the Balkan wars in the 1990s. It is only when Kosovo is visibly and finally no longer a part of Serbia that the Serbs will give up their fixation on this issue. Kosovo's independence, therefore, will not only free the Kosovo Albanians from the Serbs, it will free the Serbs from their reactionary debates."

The center-left Süddeutsche Zeitung writes:

"The voters in the urban centers of Belgrade and Novi Sad, as well as the Hungarian and Muslim minorities tipped the balance in this fateful election. For many Serbs, memories of the sanctions they suffered in the 1990s because of their leaders' warmongering are still fresh. With this vote, the majority has demonstrated that it wants integration with Europe."

"(Kostunica) abused the emotions of the people, who were unsettled by the loss of Kosovo. He tried to depict the pro-European (Tadic) as a traitor who was ready to give up the historically important battle field of Amsfeld for a few billion euros from Brussels. Kostunica's game of confrontation has not worked. And Tadic has realized that Belgrade will only be able to fight for the rights of the Serb minority in Kosovo by closely cooperating with the EU."

"The West will allow the province to declare independence because, ever since Serbia got Kosovo back after the fall of the Ottoman Empire, they have favored force over the integration of the Albanian people. … Serbia will only find normality when its political elite have freed themselves from the burden of Kosovo."

The left-leaning Die Tageszeitung writes:

"With the ongoing conflict over Kosovo, national questions take precendence over economic and social questions."

"This is a stumbling block to the development of Serbia. If voices in Europe calling for Kosovo to be sacrificed on the altar of better relations with Serbia now grow louder, then that will only cause the conflict over Kosovo to be caught in an endless loop. Instead of freeing itself from the past and finally making peace with equal neighbors, Serbia will be chained forever."

"Those who wish to strengthen the civil and future-oriented Serbs, have to cut the ties now. Compromises and backing away won't help here."

The business daily Handelsblatt writes:

"Serbia is a divided land … Almost half of the voters have nationalist inclinations and see themselves as the losers of Belgrade's modernization policies. The looming secession of Kosovo is playing into their hands. The task of convincing them of the advantages of closer ties with Europe will be a difficult one for the president."

"The fault lines of the break up of the former Yugoslavia run through Serbia. Less than 10 years ago, NATO bombs were falling on the territory, and war criminals wanted by the Hague still live under Belgrade's protection."

"Serbia has to develop new perspectives in order to deal with its past. That is one of Tadic's most important tasks. Serbia will only be able to find internal peace and build a constructive cooperation with the EU if he succeeds in putting in motion a policy of reconciliation and of overcoming the differences between himself and Prime Minister Kostunica. There are a lot of political and economic issues that must still be dealt with in the Balkans. Brussels should take advantage of the present circumstances and underpin the rather half-hearted gestures toward Serbia with deeds. Only then can the EU succeed in convincing the skeptics."