In an interview with Deutsche Welle broadcaster, he said Russia was considering testing the reliability of NATO's Article 5, which states that an attack on one ally must be treated as an attack on all.

"We very much hope this is not true and that we will not be put in the difficult position of it being tested. However, we must assume that Russia wants to test us, to put the unity of the West to the test," Kahl said.

The timing of a Russian test of NATO's collective defence clause depends on the course of the war in Ukraine, according to Kahl.

If the war ends earlier than 2029 or 2030, this would enable Russia to use its technical, material and personnel resources to build up a threat against Europe sooner, he noted.

"It is also possible that a concrete threat or blackmail attempt from Russia against Europeans could occur earlier than previously calculated," Kahl said.

"An early end to the war in Ukraine would enable the Russians to direct their energy where they actually want it, namely against Europe."

Kahl said Russia envisions a future world order resembling the situation in Europe in the late 1990s, with NATO's protective presence pushed back and Russia's sphere of influence expanding westward — ideally without an American presence in Europe.

© Deutsche Presse-Agentur GmbH