BERLIN, September 27 (RIA Novosti) - Germany will hold parliamentary elections on Sunday, with Chancellor Angela Merkel's Christian Democratic Union and the center-left Social Democrats, whose candidate is Foreign Minister Frank-Walter Steinmeier, being the main challengers.

Opinion polls have given the chancellor's conservative bloc about a ten-point lead as Merkel, 55, and Vice-Chancellor Steinmeier, 53, tried to win over undecided voters on Saturday, the last day of the election campaign.

The common faction of the Christian Democrats (CDU) and their sister party Christian Social Union of Bavaria (CSU) had 222 seats (36.3%) and Social Democrats (SPD) had 221 seats (36.2%) in the previous parliament, making a "grand" ruling coalition in the Bundestag.

Merkel's party has lost some of its supporters lately, and the chancellor, who would like to form a new center-right coalition with the pro-business Free Democrats, could have to reenter an old right-left coalition that has ruled for four years, which could ruin her plans to have taxes cut and state influence in the economy reduced.

The German parliament has at least 598 seats but in some circumstances, "overhang" seats are also distributed. There were 13 such seats in the previous parliament.