Two senior US Republican lawmakers have criticised a decision by the Pentagon to cut 5,000 US troops stationed in Germany, saying it risked undermining deterrence and would send the wrong signal to Russia.

Roger Wicker and Mike Rogers, who chair the Senate and House armed services committees respectively, said that rather than being withdrawn, those troops should be moved further east.

Pentagon spokesperson Sean Parnell on Friday said the move followed a thorough review and recognised "theater requirements and conditions on the ground".

On Saturday, President Donald Trump said further cuts could take place, without providing details. The US has more than 36,000 active duty troops in Germany.

Germany's defence minister said the Pentagon decision was "foreseeable".