LONDON (Reuters) - British Prime Minister Boris Johnson warned Russian President Vladimir Putin in a call on Monday that any destabilising action against Ukraine would be a strategic mistake with significant consequences, Downing Street said.

       "The Prime Minister emphasised the UK's commitment to Ukraine's territorial integrity and sovereignty, and warned that any destabilising 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."

       (Reporting by Guy Faulconbridge and Kate Holton. Editing by Andrew MacAskill)