BERLIN - Conservative Chancellor Angela Merkel goes head to head with Social Democrat (SPD) challenger Frank-Walter Steinmeier in a TV debate later on Sunday which may help determine the outcome of Germany's election on September 27.

With the SPD trailing Merkel's conservatives in the polls by 11-14 points, the onus is on Steinmeier to land a punch on Merkel and win over undecided voters. Analysts say up to 40 percent have still to make up their mind.

The TV debate is Steinmeier's big chance because he will reach millions of people, political scientist Karl-Rudolf Korte told Bild am Sonntag newspaper.

Around 20 million people, or a quarter of the population, is expected to tune in to the 90-minute U.S.-style clash shown on four channels which starts at 8.30pm (1830 GMT).

Coalition arithmetic means the debate could be crucial.

Despite the conservatives' lead over the SPD, it is far from certain whether Merkel will win enough votes to form a coalition with her desired partners, the pro-business Free Democrats (FDP).

Such an alliance would herald a shift to the right in Europe's biggest economy and open the way to tax cuts and an extension in the operation of some nuclear plants.

To avoid that, the SPD has to mobilize its traditional supporters, say analysts.

But Germans are having trouble distinguishing between the policies of the two main parties, not least because they have shelved their differences in the last four years to stay in power together in a grand coalition.

Aware they may end up having to share power again, Merkel and Steinmeier have largely avoided personal attacks and the campaign has been less combative than usual.

FOCUS ON ECONOMY

Merkel is banking on voters giving her credit for her handling of the financial crisis.

The SPD has promised to create 4 million jobs by 2020 and attacked Merkel's conservatives for lacking ambition in their election vows which have centered on vague tax cuts.

Steinmeier may try to seize the initiative on the contentious issue of Germany's role in Afghanistan on Sunday.

Der Spiegel reported that he had drawn up a 10-point plan for the withdrawal of the roughly 4,200 German troops deployed in Afghanistan by 2013. That could prove popular as most Germans want their soldiers to come home.

With the exception of the far-left Left party, there has until now been a political consensus backing the deployment.
International and domestic criticism of an airstrike called in by German troops in northern Afghanistan this month that killed scores of people, including civilians, has catapulted the issue into the election campaign.

The TV debate attracted 21 million viewers four years ago when then SPD Chancellor Gerhard Schroeder succeeding in closing the gap on Merkel in opinion polls and nearly caught her in the election.

But with neither Merkel nor Steinmeier known for their charisma, one TV channel has opted to capitalize on the lack of interest in debate and is broadcasting The Simpsons movie instead.

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