A statement by US President-elect Donald Trump that Nato is "obsolete" has caused "worry" in the alliance, Germany's foreign minister says.
Frank-Walter Steinmeier said it was a contradiction of comments made days ago by Mr Trump's incoming defence chief.
Mr Trump also said German Chancellor Angela Merkel had made "a catastrophic mistake" by admitting more than one million migrants.
And he threatened German car makers with high import tariffs.
Shares in BMW, Volkswagen and Daimler fell after he warned that cars built in Mexico, where they have invested in factories, would be taxed at 35% if exported to the US.
BMW said the company would stick to its plans to open a Mexican plant in 2019.
Mr Trump was giving an interview in New York to two British and German newspapers, the Times and Bild, at Trump Tower.
Few surprises: analysis by BBC Berlin correspondent Jenny Hill
Donald Trump's comments have caused dismay, concern - but perhaps not surprise - in Berlin. Few expected the new transatlantic relationship to echo the warm and trusting alliance nurtured by Angela Merkel and Barack Obama, who was a vocal supporter of Mrs Merkel's refugee policy.
There is anger, too. Germany's outspoken Vice-Chancellor Sigmar Gabriel retorted that the migrant crisis was the result of "faulty, interventionist American policies in the Mediterranean and Middle East".
That Mr Trump should take aim at Germany's car manufacturers has also raised eyebrows, though few here believe his Congress would approve the 35% tax he appears to be threatening to impose on imported vehicles.
Germans were largely unimpressed by Mr Trump during his election campaign and now, despite his own German heritage, the president-elect is doing little to endear himself.
Mr Trump called Nato "obsolete" because it "wasn't taking care of terror".
Nato, he said, was "very important" to him but only five of its 28 member-states were paying their fair share and that, he said, was "very unfair to the United States".
Figures released by Nato show that just five member-states met or surpassed its defence spending goal - 2% of GDP - last year.
Speaking in Brussels after consulting Nato Secretary-General Jens Stoltenberg, Mr Steinmeier said the president-elect's comments had caused "worry and concern".
"This is in contradiction with what the American defence minister said in his hearing in Washington only some days ago," the German foreign minister said.
At his Senate confirmation hearing last week, Mr Trump's choice for defence secretary, Gen James Mattis, had described Nato as central to US defence, and had accused Russian President Vladimir Putin of trying to "break" the alliance.
Later, Mr Steinmeier was quoted by Reuters news agency as saying: "I've spoken today not only with EU foreign ministers but Nato foreign ministers as well and can report that the signals are that there's been no easing of tensions."
Only last week, the US deployed 3,000 soldiers, 80 tanks and hundreds of armoured vehicles to Poland in a move by President Barack Obama to reassure Nato allies concerned about a more aggressive Russia.
President Putin's official spokesman, Dmitry Peskov, said on Monday it was too early to give a full response to a suggestion by Mr Trump that US sanctions against Russia over Ukraine could be dropped in return for a nuclear warhead reduction deal.
Mr Peskov also denied reports Mr Putin and Mr Trump were going to hold a summit in Iceland.
EU 'vehicle for Germany'
Mr Trump said the EU had become "basically a vehicle for Germany".
Referring to the German chancellor's response to an influx of refugees and other irregular migrants in 2015, he said: "I think she made one very catastrophic mistake and that was taking all of these illegals..."
Mrs Merkel responded by saying the EU had to take responsibility for itself. "We Europeans have our fate in our own hands," she said in Berlin.
Her Vice-Chancellor, Sigmar Gabriel, said Europeans should show more self-confidence in dealing with Mr Trump. "We're not weak and inferior," he told Bild.
Mr Trump linked the migrant issue with Brexit, suggesting it was a reason UK voters opted to leave the bloc.
He promised a quick trade deal between the US and the UK after he takes office on Friday but a European Commission spokeswoman reiterated that the UK would not be allowed to engage in formal talks involving a trade deal with the US until 2019, after leaving the EU.
Elsewhere in his interview, Mr Trump
- Said Russia's military intervention in Syria had been "a very bad thing" which had created a "terrible humanitarian situation"
- Said Afghanistan was "going badly" while the offensive to retake Mosul from so-called Islamic State in Iraq had turned out to be a disaster
- Likened the US-led invasion of Iraq in 2003 to "throwing rocks into a beehive"
- Promised to "keep" Twitter as president, saying, "I can go bing, bing bing" and respond to "dishonest" news
A note on terminology: The BBC uses the term migrant to refer to all people on the move who have yet to complete the legal process of claiming asylum. This group includes people fleeing war-torn countries such as Syria, who are likely to be granted refugee status, as well as people who are seeking jobs and better lives, who governments are likely to rule are economic migrants.