US threatens to withdraw troops from Germany over insufficient NATO spending

"It is offensive to assume that the US taxpayers continue to pay for more than 50,000 Americans in Germany but the Germans get to spend their (budget) surplus on domestic programs," Grenell told the dpa news agency on Friday.

Trump has publicly criticized German and other NATO members that have failed to hit a target of spending 2 percent of their gross domestic product on defense.

He has been particularly critical of close ally Germany, Europe’s largest economy, as well as Merkel personally.

Germany's fiscal plans foresee the military budget of NATO's second-largest member rising to 1.37 percent of output next year before falling to 1.24 percent in 2023.

Eastern European countries like Poland and Latvia, fearful of Russia, have raised their military spending to the 2 percent target, from Trump who wants Germany to do the same.

US complaints about Germany's defense spending pre-date Trump, but Berlin’s relations with Washington have deteriorated since he became president over a range of issues, including the Iran nuclear agreement, the NordStream 2 gas pipeline from Russia to Germany, and trade tariffs.

The United States has about 35,000 troops stationed in Germany at five US Army garrisons, and an additional 17,000 civilian employees to support them. It is believed the US also has nuclear weapons in Germany.

US Ambassador to Poland, Georgette Mosbacher, has made a similar criticism of Germany's reluctance to commit more financial resources to NATO.

"Poland meets its 2% of GDP spending obligation towards NATO. Germany does not. We would welcome American troops in Germany to come to Poland," she wrote on Twitter on Thursday.

"President Trump is right and Georgette Mosbacher is right," Grenell told dpa. "Multiple presidents have asked Europe's largest economy to pay for its own defense. This request has been made over many years and by many presidents."

Grenell earlier this month criticized Germany for refusing to join a planned US naval mission in the Strait of Hormuz, close to Iran.