EU and Nato allies have swung behind the Biden administration’s assessment that Russia may be poised to invade Ukraine following unprecedented sharing of US intelligence on Moscow’s military preparations.

Weeks of sustained US diplomatic engagement with European governments, backed by a sharing of intelligence normally reserved for its closest allies, have helped convince some previously skeptical capitals, including Berlin, that the Kremlin could soon order its troops into Ukraine. The effort has galvanized support for the need for robust sanctions threats to deter the Kremlin.

Joe Biden will warn Vladimir Putin against any invasion in a planned video summit on Tuesday, with the full backing of Nato and the EU for retaliatory measures, European defense and security officials told the Financial Times.

Russia could be planning to invade Ukraine “as soon as early 2022”, a Biden administration official said on Friday, adding that half the military units that would be involved in such an offensive had arrived near Ukraine’s border over the past month.

The US decision to share its intelligence among European states and issue public warnings stems from Washington’s hope that by cementing western support for sanctions, it would underline to Moscow the costs of any aggression. The details of threatened sanctions and other countermeasures are still under discussion.