Under German law, citizens may only carry a German passport. Holding dual nationality automatically disqualifies a person from German citizenship and thus the right to vote. The only exceptions are when the second passport is from another European Union country or if a citizen has obtained special permission.

The interior ministries of Germany's 16 states said this week that nearly 20,500 of the some 600,000 Turkish-German voters were affected by the new rules passed by parliament five years ago and would not be able to vote Sunday.

But Turkish associations in Germany said the figure could be as high as 50,000 nationwide.

Kenan Kolat, vice president of the Turkish Community in Germany said many Turks had been completely ignorant of the regulation and weren't aware that the Turkish consulates in Germany had continued to register them as "Turkish nationals" after they had acquired German passports.

But interior ministries in several German states are not buying the argument, stressing that Turks who were naturalized, were aware they couldn't take on dual citizenship.

In the conservative-led southern state of Bavaria alone, some 6,700 Turkish-Germans were believed to have two passports.

"Those who vote anyway will be breaking the law," state Interior Minister Günther Beckstein said.

Turkish vote important for Schröder

With polls showing a tight race, the Turkish vote has emerged as a potentially important factor, particularly for Chancellor Gerhard Schröder's Social Democrats (SPD) and their coalition partners, the Greens. Germany's Turks have traditionally been loyal to Schröder's party.

Though the number of Turkish voters may seem insignificant in an overall voting population of around 62 million, the Turkish-German vote could prove crucial in the event of a close electoral outcome. In the last election in 2002, Turkish votes came in handy when just 6,027 votes saved Schröder from defeat.

It's little surprise then that Schröder -- whose Social Democrats are strong backers of Ankara's bid to join the European Union -- has been actively wooing the Turkish-German community in the weeks leading up to the election.

This week Schröder visited the publishing house of Hürriyet, one of the Turkish-German community's most influential newspapers, praising Turks' contribution to German society and stressing the importance of bringing Turkey into the EU.

Reflecting the SPD's attempts to attract Turkish-German votes, Germany's top-selling newspaper, Bild, this week splashed a photo of Schröder speaking beneath a giant Turkish flag and asked "Will Turks decide the election?"

A survey released by Hürriyet showed that 77 percent of Turkish-Germans plan to vote for the Social Democrats against just 4.8 percent for Angela Merkel's conservative Christian Democrats, who have firmly ruled out accepting Turkey in the EU and offered it a so-called "privileged partnership" instead.

The Greens tallied 9.2 percent versus 7.8 percent for the Left Party, a new alliance comprising disgruntled Social Democrats and former communists. The free-market liberal FDP, Merkel's preferred coalition partners, polled 1.2 percent.