Europe should not fear a renewed US focus on Asia and must increasingly look after its own backyard militarily without its historic ally, Germany's defence minister said on Friday.

"Europeans should not look at the strategic re-orientation of the Americans with apprehension. There is every reason to be calm and confident," Thomas de Maiziere said, opening the Munich Security Conference.

As Washington looks east, "Europe must be able to assume responsibility, including military responsibility for itself and for security in its immediate neighbourhood," the minister added.

"Europe will increasingly have to take care of its own security."

Last November, President Barack Obama made a landmark speech in Australia where he shifted his nation's strategic focus to the Pacific.

"Here is what this region must know. As we end today's wars, I have directed my national security team to make our presence and missions in the Asia-Pacific a top priority," Obama said.

Last month, the United States announced plans to withdraw two of its four army brigades stationed in Europe in 2014.

There are some 81,000 US troops in Europe, according to Pentagon data released in September 2011, about half of them stationed in Germany.

De Maiziere said there was "no reason for complaint" about this withdrawal.

"Europe and Germany will continue to be the greatest and most important military location for US troops outside their country. We are seeing a shift from quantity to quality," he added.

Speaking at a US base in Germany, US Defence Secretary Leon Panetta also sought to assure Europeans of Washington's continued commitment.

"I want to make clear to our European and NATO allies that we'll maintain a significant presence here in Europe," said Panetta.

"Here in Europe, we'll have the largest troop presence than anywhere else in the world ... We want to maintain our presence everywhere, that's a very important part of our security," added the secretary.