"We think that the US presence in Germany is important for the security not just of Germany but also for the security of the United States and especially for the security of Europe," Heiko Maas said during a visit to Poland a day after Trump's announcement.

Trump said he was cutting the numbers because Germany was "delinquent" in contributions to NATO and had treated the United States "badly" on trade.

Trump told reporters there are 52,000 US soldiers stationed in Germany and he will bring this number down to 25,000.

But according to the Pentagon, there are are only between 34,000 and 35,000 US soldiers permanently stationed in Germany. Rotation of units means the overall number can only temporarily top 50,000.

Maas said Germany had not been given any details on when and how the redeployment might take place.

"Neither the State Department nor the Pentagon has been able to provide any information about this," he said, adding that any changes to Europe's security architecture "definitely need to be talked about".

NATO chief Jens Stoltenberg on Tuesday also said that US troops in Europe made both sides of the Atlantic safer.

Defence ministers from the alliance will discuss Trump's plans during video talks on Wednesday and Thursday.

The move has been criticised as weakening America's commitment to European defence as well as its ability to wield influence in the Middle East and Africa.

US troops have been stationed in Germany since the end of World War II, reaching a peak during the Cold War.

But the resurgence of Russia's military ambitions under President Vladimir Putin has given the US presence new importance.

Speaking at a joint press conference with Maas, Polish Foreign Minister Jacek Czaputowicz said his government had been in discussions about boosting the number of US troops in Poland, but the two issues were separate.

"I want to underline that these talks (with the US) have no connection with the recent US declarations and US-German relations concerning the presence of, or reduction of, US forces in Germany," he said.

"From our standpoint, US forces in Germany also serve our security. We would want that presence in Germany to be continued."