Germany's new defence minister wants to create a more family-friendly army by making it easier for soldiers to work part-time and extending childcare, she told a Sunday newspaper.

"My goal is to make the German armed forces into one of the most attractive employers in Germany," Ursula von der Leyen, Germany's first female defence minister, said.

"In doing so, the most important issue is the compatability of employment and family," the 55-year-old, mother-of-seven said in an interview with Sunday's Bild newspaper.

Von der Leyen's move from the labour to defence portfolio came as a surprise when Chancellor Angela Merkel's new cabinet under her "grand coalition" with the Social Democrats (SPD) was unveiled four weeks ago.

Viewed as an up-and-coming possible successor to Merkel, von der Leyen lost no time in visiting German troops in Afghanistan a few days before Christmas and revealed in the Sunday interview she had been tapped for the job only five days before being sworn in with the rest of the cabinet.

"Anyone who, for example, uses the option of a three- or four-day week while raising a family must still have career prospects," she told Bild.

Among the reforms, she said she was also considering a system whereby overtime could be saved up and then used for looking after small children or elderly parents.

She also wants to study the army's system of transferring soldiers every two to three years, she said. "A career in the armed forces must not mean as a rule: always on duty and every few years a move," von der Leyen said.

And she added that widening childcare provision would be one of the first measures looked at.

"We need a flexible system of childcare across the armed forces," she said, calling for the provision of out-of-hours care, before or after the normal working day, beyond that offered by barrack nurseries.

Opposition politicians from the ecologist Greens and far-left Linke party voiced financing doubts and scepticism.

"There are no part-time wars and no family-friendly military missions," Inge Hoeger, of the Linke party said.

SPD defence expert Hans-Peter Bartels however told Monday's Tagesspiegel newspaper that von der Leyen's approach was "right and overdue", while the Bundestag lower house of parliament's army expert welcomed the move.

"Attractiveness, and family-friendliness is part of that, is a decisive building block in the realignment of the armed forces," Hellmut Koenigshaus told Monday's Handelsblatt business daily.

Von der Leyen, who was family affairs minister in Merkel's first cabinet, has been credited with driving social reforms, many borrowed from the centre-left opposition, including expanding childcare and granting new fathers paid leave.

Her comments come amid a debate in Germany about how to better combine family and professional life, as Europe's top economy grapples with an ageing and shrinking population and tries to boost the birthrate and lure women back to work.

New Family Minister Manuela Schwesig, a Social Democrat, has proposed cutting the work week for parents of young children, possibly to 32 hours, and using taxes to help fund the proposal.