Russia has revoked the accreditation of six British diplomats, accusing them of spying, Russian media report.
Meanwhile, President Vladimir Putin has warned the West against allowing Ukraine to use long-range weapons to target Russia.
Putin said Moscow would take “appropriate decisions” if Nato allowed Kyiv to strike Russian territory.
UK PM Keir Starmer – who is due to meet President Biden in Washington – brushed aside the warning, saying Ukraine had the right to defend itself.
But he added that he did not seek conflict with Moscow.
-BBC