The troops will be deployed by September 2020 -- adding to more than 33,000 US troops already there -- said US Army Europe, which called it "a display of our continued commitment to NATO and our collective resolve to support European security".

US Ambassador Richard Grenell said that "Americans are committed to strengthening the transatlantic alliance and President Trump's promise to increase US defence capabilities means the alliance is stronger today".

German Defence Minister Ursula von der Leyen called the new deployments "a welcome sign of the vitality of transatlantic relations" and "a commitment to common security".

Trump has long complained that European NATO members do not pay enough for their own defence, singling out Germany for particular criticism.

At a NATO summit in July, Trump called Germany "a captive of Russia" because of its energy links and a major new gas pipeline project in the works.

NATO allies agreed at a summit in Wales in 2014 to move towards spending two percent of GDP on defence by 2024. But Germany, Europe's biggest economy, spends just 1.2 percent, compared with 3.5 percent for the US.

The US Army Europe statement said the force structure change was a result of a wider 2017 directive to build up the ranks.

"As the US Army grows, a significant portion of that growth will take place in Europe as the mission to defend NATO allies and deter aggression continues to be a priority," it said in a statement.