In a phone call on Monday, British Prime Minister Boris Johnson warned Russian President Vladimir Putin that any destabilizing action against Ukraine would be a strategic mistake with serious consequences, according to Downing Street.

"The Prime Minister emphasized the UK's commitment to Ukraine's territorial integrity and sovereignty, and warned that any destabilizing action would be a strategic mistake that would have significant consequences," a spokesman said.

"He expressed the United Kingdom's deep concern over the build-up of Russian forces on Ukraine's border, and reiterated the importance of working through diplomatic channels to deescalate tensions and identify durable solutions."

PM Boris Johnson's address to the COP26 Forests & Land-use event: 2 November 2021 - GOV.UK