Kyiv declared a nationwide state of emergency and was braced for an all-out invasion following a Kremlin declaration that rebel leaders in eastern Ukraine had requested military assistance.
The White House said the plea from Russian-backed separatists was an example of the “false-flag” operation the West was expecting Vladimir Putin would use to strike.
US Secretary of State Antony Blinken said it is possible Russian forces commence an invasion of Ukraine before the night is over.
He told NBC News: “Russia has positioned its forces at the final point of readiness across Ukraine’s borders to the north, to the east, to the south. Everything seems to be in place for Russia to engage in a major aggression against Ukraine.
“I can’t put a date or an exact time on it, but everything is in place for Russia to move forward.”
Under increasing pressure to go further on sanctions against those supporting the Russian president, Mr Johnson is expected to join a virtual meeting of G7 leaders on Thursday.
Washington confirmed the US president will participate in the call after Mr Biden increased his economic action against Moscow by targeting measures against the company that built the Nord Stream 2 gas pipeline to Germany.
Ukrainian President Volodymyr Zelensky made an emotional televised address in…