BERLIN (Reuters) - It is the most coveted role in German politics, but for Frank-Walter Steinmeier being foreign minister is rapidly turning into a nightmare.

Seen as a rising star of the centre-left Social Democrats (SPD) when he took over from Joschka Fischer two months ago, the white-haired, 49-year-old confidant of former Chancellor Gerhard Schroeder has been buffeted by scandal since taking office.

Steinmeier has weathered the storm so far. But he is struggling to exploit the high-profile post as a springboard to nationwide popularity, as his predecessors Fischer and Hans-Dietrich Genscher did so effectively.

"Steinmeier has been very much on the defensive, even within his own party," said Gerd Langguth, a political scientist at Bonn University.

"Decisions he was part of as a member of the previous government have caught up with him again and again."

A furore over the alleged CIA abduction and imprisonment of German citizen Khaled el-Masri blew up only two weeks after Steinmeier moved into the Foreign Ministry building at 1 Werderscher Markt street in central Berlin.

The Schroeder government was accused of hushing up the kidnapping and as a key player in the old administration -- Steinmeier was Schroeder's chief of staff -- the new foreign minister found himself hit by a media and opposition backlash.

He dodged that bullet, but then found himself engulfed in another scandal, also linked to Schroeder.

Media reports alleged earlier this month that two German agents who were in Iraq during the 2003 U.S. invasion gathered information on bombing targets for Washington and acted as scouts for an air raid intended to kill Saddam Hussein.

Steinmeier, who had responsibility for German intelligence at the time, has denied the reports, which if confirmed would discredit the Schroeder government by exposing its anti-Iraq war stance as a sham.

He is now leading a battle to prevent a parliamentary inquiry into the affair, which he has denounced as a product of "scandal mongering".

Hostage hot seat

The troubles for Steinmeier, whose reputation for efficiency, hard work and behind-the-scenes manoeuvring earned him the nicknames "Chancellor Whisperer" and "Dr Flawless", may not end there.

Over the weekend, German magazine Focus reported that ransom money allegedly paid by the government last month to win the freedom of Susanne Osthoff, a German citizen kidnapped in Iraq, was found on Osthoff by German officials after her release.

Steinmeier, the magazine said, had ordered "absolute secrecy" on the ransom discovery.

If confirmed, the report would be a double embarrassment for him -- first because Berlin wants to avoid admitting it pays ransoms and second because it would suggest Osthoff was in cahoots with her abductors and duped the government.

"The story is full of inconsistencies that must be cleared up," demanded leading conservative Wolfgang Bosbach in German daily Die Welt.

A poll for Der Spiegel magazine on Sunday showed that only 37 percent of Germans would like to see Steinmeier play an important role in German politics in the future.

That compares to an 85 percent rating for Steinmeier's boss, new Chancellor Angela Merkel, and a 72 percent score for Matthias Platzeck, the head of Steinmeier's SPD.

It pales in comparison to the ratings of his predecessor Fischer, for years Germany's most popular politician, and the mild, modest Genscher, who served as foreign minister for nearly two decades and was a favourite of Germans in the east and west.

The SPD had similar hopes for Steinmeier, when they tapped the longtime Schroeder loyalist to run the most high-profile ministry in Merkel's bipartisan "grand coalition".

As foreign minister, the reasoning went, Steinmeier could ensure continuity in Schroeder's foreign policy, stay out of damaging domestic battles, and emerge as a potential challenger to Merkel in the next election.

Instead, Merkel has overseen a wholesale shift in German foreign policy over the past two months, helping broker a European Union budget deal, thawing relations with Washington and taking a decidedly cooler approach with Russia.

Steinmeier's time may still come. He has shown a knack for toughing out the scandals and has looked capable, even comfortable, in his new post.

But soaring to the heights envisioned for him by his party may prove more difficult than many expected.