German President Frank-Walter Steinmeier has strongly criticized the US foreign policy under President Donald Trump and urged the world not to let the world order disintegrate into a "den of robbers," Reuters reports.

In unusually strong remarks, which appeared to refer to actions such as the US ousting of Venezuela's President Nicolas Maduro at the weekend, the former German foreign minister said global democracy was being attacked as never before.

Describing Russia's annexation of Crimea and the military operation in Ukraine as a watershed, Steinmeier said the US behavior represented a second historic rupture.

"Then there is the breakdown of values by our most important partner, the USA, which helped build this world order," Steinmeier said in remarks at a symposium.

"It is about preventing the world from turning into a den of robbers, where the most unscrupulous take whatever they want, where regions or entire countries are treated as the property of a few great powers," the German president said.