U.K. Prime Minister Boris Johnson says western allies will respond to any Russian attack on Ukraine with economic sanctions "heavier than anything" they've imposed before.
Johnson discussed the buildup of Russian troops on the border with Ukraine with U.S. President Joe Biden and other European leaders during an urgent video call on Monday.
Giles Gibson reports from London.
IN: "As the British…"
OUT: "...Giles Gibson, London."
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