BERLIN: German Chancellor Angela Merkel faces off in a live television debate Sunday night against challenger Frank-Walter Steinmeier, who needs a strong performance to lift his struggling center-left party's prospects two weeks before elections.

The prime-time debate is being shown on four public and private channels.

It is the only head-to-head duel of a campaign notably short so far on passion and personal attacks between Merkel and Steinmeier, currently her foreign minister and vice chancellor.

A good Merkel performance would strengthen her hopes of ending an awkward "grand coalition" with Steinmeier's Social Democrats after the Sept. 27 election. In a second term, Merkel aims to form a new center-right government with a pro-business opposition party, the Free Democrats.

Steinmeier needs to score points against Merkel to prevent that and boost his own, currently slim, chances of taking the top job.

Polls give Merkel's Christian Democratic Union and its Bavaria-only sister, the Christian Social Union, a lead of 12 percentage points or more over the Social Democrats. They show a majority, though not a big one, for a center-right alliance.

Nearly 21 million people in Germany, a nation of 82 million, watched Merkel debate then-Chancellor Gerhard Schroeder, a Social Democrat, four years ago.

Schroeder's strong performance was credited with helping narrow a deficit against the conservatives. The indecisive election outcome resulted in the "grand coalition" of Germany's biggest parties.

Merkel looks better placed this time. She is a popular incumbent and, in Steinmeier, faces an opponent who lacks Schroeder's rhetorical gifts.

"The ball is in Steinmeier's court," given his party's poll deficit, said Frank Brettschneider, a communications scientist at the University of Hohenheim.

"His greatest chance lies in presenting the (party) as a guarantor of social justice," in contrast to what a center-right government might do, he added.

Merkel's conservatives are pledging tax relief to stimulate the economy, but haven't specified when. Steinmeier's party says that isn't feasible when the government is racking up debt to deal with the crisis.

Steinmeier also is defending a Schroeder-era plan to shut down all Germany's 17 nuclear plants by 2021. The "grand coalition" has stuck with it, but Merkel wants to extend the life of some reactors.

There are limits to how hard the two can attack each other. They worked together on bank rescues and stimulus packages in the crisis; both pushed for the sale of General Motors Co.'s Opel unit to auto parts maker Magna; both back German troops' mission in Afghanistan.