BERLIN - Chancellor Angela Merkel's hopes of forming a new center-right government suffered a blow on Friday, two days before Germany's federal election, as a new opinion poll showed her just short of her goal.

While she attended a G20 summit in Pittsburgh, her Social Democrat (SPD) challenger Frank-Walter Steinmeier delivered a rousing speech to thousands of supporters at Berlin's Brandenburg Gate, telling them: Everything is wide open.

Shortly before he spoke, al Qaeda leader Osama bin Laden warned European countries to withdraw their troops from Afghanistan in an audio tape with both English and German sub-titles that appeared timed to spook German voters before the election on Sunday.

A series of al Qaeda videos over the past week have threatened Germany with a rude awakening if the electorate backs a government that supports the mission in Afghanistan, where 4,200 German troops are stationed.

Police in the southern city of Stuttgart said on Friday they had arrested a 25-year old Turkish man they suspect of posting one of the threatening videos on the Internet.

Merkel holds a lead of 8-11 points over her SPD rivals heading into election weekend and is widely expected to win a second four-year term.

But a new poll by Forsa on Friday showed support for her conservative bloc -- the Christian Democratic Union (CDU) and Christian Social Union (CSU) -- shrinking to 33 percent, its lowest level in months.

It also put her short of her goal to form a governing majority with the business-friendly Free Democrats (FDP), a center-right partnership that would pursue tax cuts and reverse a planned phase-out of nuclear power plants in Germany.

If she does not win enough support to team up with the FDP, her conservatives would probably be forced into another awkward grand coalition with the rival SPD, a partnership which worked well during the financial crisis but which analysts say could be less stable and harmonious the second time around.

STEINMEIER VOWS TO FIGHT

In one of his most forceful speeches of the election campaign, Steinmeier vowed on Friday evening to fight to the last second for every vote.

The race is open again, everything is wide open, he told a crowd the organizers estimated at 10,000. We've caught up, we've fought and anyone who catches up can also overtake.

The Forsa poll showed 26 percent of voters were still undecided, suggesting Germany could be in for another cliffhanger election.

Merkel's conservatives saw a similar poll lead nearly vanish on election day four years ago when Steinmeier's mentor, then-Chancellor Gerhard Schroeder, mounted a furious comeback in the final days before the vote.

This time Merkel has played it safe, avoiding confrontation and counting on her strong personal popularity ratings to help her party to victory.

I will definitely vote on Sunday but I don't know which party yet, said Johannes Renner, 35, a lawyer watching the Steinmeier rally. Merkel hasn't campaigned and hasn't said anything concrete about anything. It's all been so vague.
The series of al Qaeda videos over the past week have revived memories of Islamist bomb attacks on commuter trains in Madrid in 2004, which killed 191 people three days before a general election in Spain.

Germany has stepped up security at airports and train stations in response to the threats and the U.S. State Department took the unusual step of warning Americans in Germany to be vigilant.

A spokesman for Germany's Interior Ministry said officials were examining the message from bin Laden, which did not explicitly mention Germany but alluded to the heart of Europe and used German subtitles.

We are taking this message very seriously, spokesman Stefan Paris said.

Paul Cruickshank, a fellow at the Center on Law and Security at New York University's School of Law, said the message recalled those issued by the al Qaeda leader in past years warning European allies of the United States of reprisals unless they pulled out of Iraq.

This message seems very much directed at Germany. Al Qaeda is trying to turn up the heat on Germany over Afghanistan ahead of the elections, he said.

(Additional reporting by William Maclean, writing by Noah Barkin, editing by Mark Trevelyan)

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