Trump has ordered the US military to remove 9,500 troops from Germany, a senior US official said on Friday.
"This is completely unacceptable, especially since nobody in Washington thought about informing its NATO ally Germany in advance," Peter Beyer, a member of Chancellor Angela Merkel's conservatives, told the Rheinische Post newspaper.
Following Trump's decision, German Foreign Minister Heiko Maas said in a newspaper interview that he regretted the planned withdrawal of US soldiers from Germany, describing Berlin's relationship with the United States as "complicated."