Berlin -- Angela Merkel, embarking on her second term as German chancellor this week, has been described as the world's most powerful woman despite what some decry as excessive caution -- or perhaps because of it.

Following elections on September 27, Merkel's Christian Democrats (CDU/CSU) was able to ditch her previous coalition partners, the centre-left Social Democrats (SPD) for the pro-business Free Democrats (FDP).

The 55-year-old trained physicist, who first became chancellor in 2005, has enjoyed a stellar rise from an East German pastor's daughter to Forbes magazine's world's most powerful woman four years on the trot.

She was in 2005 the first woman to govern Germany and the first politician from the former communist East to head the reunified country. She was even the youngest person to become chancellor.

Derided as a less-than-gifted public speaker, Merkel has relied on meticulous preparation, gentle humour and modest leadership to lead Western Europe's top economic power and most populous country.

But critics have accused her of passivity, letting feuds fester until a compromise emerges, and depriving the administration of a clear political course.

"Mrs Merkel knows that if she is not confrontational, she can rely on her popularity as chancellor. She has the highest popularity ratings of any chancellor in German history," Merkel biographer Gerd Langguth told AFP.

Her cautious approach also drew fire as the financial crisis whipsawed through global markets late last year, with Merkel dubbed "Madame Non" by fellow leaders expecting a bigger German stimulus effort.

Merkel has racked up a number of foreign policy triumphs including a hard-fought compromise on the EU budget in 2005 and a climate deal under her 2007 G8 presidency that earned her the admiring nickname "Miss World."

But she has stepped on toes to defend national interests, as when she brokered a deal to sell ailing carmaker Opel, a key employer, to her favoured buyer backed by Russian capital, or fought off EU emission caps on behalf of German heavy industry.

Born Angela Kasner, she left Hamburg, West Germany with her parents a few weeks after her birth in the summer of 1954 when her Protestant father decided to up sticks and work in the communist East.

Locals remember her as a brilliant student who learned compromise and discretion early on to cope as a Christian in a totalitarian state.

Merkel earned a physics doctorate and stayed out of politics until the Berlin Well fell 20 years ago, but in 1990 she joined the CDU and won a parliamentary seat in the former East Germany.

She had to endure the fond but patronising nickname "the girl" bestowed by her mentor, then chancellor Helmut Kohl, who made her minister for women's issues and later environmental affairs.

But in 2000, the frumpy newcomer rose to head the CDU when she alone had the courage to tell Kohl to quit as party chairman in a slush fund scandal.

It earned her powerful enemies in the CDU, a party dominated by Roman Catholic family men from the western part of Germany for whom she has always been something of a misfit as a twice-married childless woman from the east.

She divorced her first husband in 1982 but kept his name when she married chemist Joachim Sauer 11 years ago. Sauer is so publicity-shy he opted not to attend her inauguration as chancellor in 2005.

AFP/Expatica