The British government has warned Russia that it needs to “step back from the brink” and desist from a possible invasion of Ukraine, or oligarchs linked to the Kremlin may be subject to sanctions. Downing Street said that Prime Minister Boris Johnson will speak to Russian President Vladimir Putin on Monday afternoon, and will visit Ukraine on Tuesday for a meeting with Ukrainian President Volodymyr Zelensky. During a visit to Tilbury on Monday, Johnson said that he would tell Putin “Russia needs to step back from the brink” and an incursion into Ukraine would be “a disaster for Russia.” He said the UK supports the “territorial sovereignty” of Ukraine and he believes Ukrainians will “bitterly” defend the country against aggression. Downing Street said the prime minister would tell Putin to “take a diplomatic path” and avoid a “very costly” military action in Ukraine. “Our aim is to continue to encourage …