"We do not have for the moment any sign indicating that there is an imminent risk of a Russian invasion of Ukraine," Steinmeier yesterday said at a press conference in Oslo, while adding that the military buildup was a "threat".
"But how is the situation going to develop? It's very difficult to say," he said. "I don't even know what is going to happen in the next few days, not to mention the next weeks."
According to NATO, Russia has amassed up to 40,000 troops on the Ukrainian border.
Steinmeier called on Russia to help restore calm in eastern Ukraine where pro-Moscow militias have launched violent attacks and seized several towns in the Russian-speaking region.
He made a special appeal for the release of OSCE military observers -- four of whom are German -- who have been taken hostage by the rebels.
His comments came as both the United States and the European Union yesterday imposed new sanctions against Russia for failing to defuse the situation in Ukraine, the worst East-West crisis since the Cold War.