Russia is planning "the biggest war in Europe since 1945," British Prime Minister Boris Johnson told the BBC during an interview that aired on Sunday.
“I'm afraid to say, that the plan that we're seeing, is for something that could be really the biggest war in Europe since 1945,” he said.
He added that “people need to understand that the sheer cost in human life that that could entail not just for Ukrainians, but also for, for Russians and for young Russians.”
On the issue of sanctions, Johnson said the aim was to impact not just “the associates of Vladimir Putin but also all companies, organizations of strategic importance to Russia.”
“We're going to stop Russian companies raising money on UK markets and we’re, even with our American friends, going to stop them trading in pounds and dollars that will very hard,” he said.
Speaking at the Munich Security Conference in Germany on Saturday, Johnson said that in preparing to invade Ukraine, Russian President Vladimir Putin is “gravely miscalculating," adding that Moscow would have “absolutely nothing to gain from this catastrophic venture and everything to lose.”
Johnson urged Moscow to de-escalate tensions before it’s too late.
I fear that a lightning war would be followed by a long and hideous period of reprisals and revenge and insurgency, and Russian parents would mourn the loss of young Russian soldiers, who in their way are every bit as innocent as the Ukrainians now bracing themselves for attack," he said.
Johnson said, “We don’t fully know what President Putin intends,” adding that “the omens are grim and that is why we must stand strong together.”
Johnson's remarks come a day after US Defense Secretary Lloyd Austin said Russia was "moving into the right positions to conduct an attack."
"They're uncoiling and now poised to strike," Austin said, speaking from Vilnius, Lithuania on Saturday.
"If you look at the stance he is in today, it's apparent [Putin] has made a decision and they are moving into the right positions to conduct an attack.”
Echoing US President Joe Biden's assertion that Putin had made up his mind on invading, Austin added that the US would pursue a diplomatic solution "until the very last minute, until it's not possible."
However, Ukraine's President Volodymyr Zelensky has countered Western leaders' heightened claims that a Russian invasion is imminent.
When asked about the aggressive use of US intelligence to dissuade Putin from invading Ukraine, Zelensky said he was "grateful for the work that both of our intelligence has been doing. But the intelligence I trust is my intelligence.
"I trust Ukrainian intelligence who ... understand what's going on along our borders, who have different intelligence sources and understand different risk based on intercepted data... this information should be used," Zelensky told CNN's Chief International Anchor Christiane Amanpour in a one-on-one interview at the security conference on Saturday.
He continued: "We are not really living in delusion. We understand what can happen tomorrow ... just putting ourselves in coffins and waiting for foreign soldiers to come in is not something we are prepared to do."
Zelensky then called for international partners to support Ukraine by investing in the country. "Strengthen our arms... our economy. Invest in our country. Bring your business in.
"We are not panicking, we want to live our lives," he added.
CNN's Ross Levitt, Karen Smith, Maegan Vazquez, Kevin Liptak, Betsy Klein, Sam Fossum, Emmet Lyons and Lauren Said-Moorhouse contributed reporting to this post.
This post has been updated.