Joe Biden, the US president discussed the Ukraine situation with Ursula von der Leyen, the European Commission president, at the White House on Wednesday.  Kamala Harris, the US vice president, met Emmanuel Macron, the French president, in Paris this week.

Last week, Mr Biden sent William Burns, the CIA director and former US ambassador to Russia, to Moscow, where he spoke to Mr Putin by phone and conveyed the US president’s concerns.

US officials warned Moscow against making a “serious mistake” amid the build-up of troops. They have shared intelligence on the Russian movements with allies and briefed them on the possibility of a military operation.

The Kremlin has denied it is an aggressor and has accused the US and its Nato allies of provocation. Mr Putin repeated that message in a call with Angela Merkel, the German Chancellor, on Thursday.

Russia’s defence ministry claimed the incident involving the British plane was part of a wider uptick in military activity by the US and its allies. Moscow said a British Boeing RC-135 Rivet Joint reconnaissance plane was trying to get close to Crimea.

It said the Russian military scrambled a Sukhoi SU-30 fighter jet to intercept and the British plane changed course away from Crimea after being approached.

Moscow – which published pictures of the UK plane – also claimed increased Nato activity in the Black Sea region had involved two US warships and four Nato spy planes, including the British one, in a 24-hour period.