The prime minister warned that “the evidence is clear” that Russia was planning an attack, which could take place within 48 hours, as he called on Mr Putin to reconsider.
And Mr Johnson called for a response to Western sanctions, saying “Europe needs to reduce its dependence on Russian gas supplies to Germany, including the Nordstream pipelines.”
This came as Foreign Secretary Liz Truss, who chaired a meeting of the UK government’s Cobra Emergency Committee, urged the British to leave Ukraine via trade routes while still facing the threat of “Russian invasion”. Can cause.
Russia has accused Britain and the United States of a propaganda campaign and insisted it was ready to continue talks.
Speaking to reporters at the Rosith Naval Dockyard during a visit to Scotland on Monday, Mr Johnson urged the Russian leader to consider the economic and political consequences if he attacked Ukraine.
The prime minister said “the world needs to learn a lesson from 2014” when not much was done to get rid of Russian gas and oil after the annexation of Crimea.
“This is a very, very dangerous, difficult situation. We are on the brink of disaster, but there is still time for President Putin to step back,” he said.
“I think what all European countries need to do now is to get the Nord Stream out of the bloodstream – a hypodermic drip feed of Russian hydrocarbons that continues to drive many European economies.”
“We need to find alternative energy sources; and be prepared to impose some very, very serious economic consequences on Russia.”
The prime minister was briefed by British intelligence chiefs on the latest intelligence developments and has cut short a planned visit to northern England to lead a Cobra meeting on Tuesday.
He says his defense minister, Ben Wallace, is right that the West should unite against Russian aggression.
Asked if he agrees with Mr Wallace’s claims that the crackdown on Mr Putin so far has been a “wave of Munich” and flattery, Mr Johnson said: “I think the Secretary of Defense is right. It is true that we must be strong, and we must be determined and united.
Russia-Ukraine conflict: Britain’s defense minister says ‘voices in Munich’
“I think it’s very important that we all stand together and show a united front, especially when it comes to economic sanctions.
“The United Kingdom, as you know, has been at the forefront of mobilizing our allies for a tough package of sanctions.
“It’s very important that the West be united, especially NATO. It’s very encouraging to see the way countries are coming together.
The pipelines are a source of tension among Western allies who have imposed sanctions on Russia, with US President Joe Biden insisting that if Putin invaded Ukraine, Nord Stream 2 would be blocked. Germany has so far refused to say what action it will take.
Asked if he would travel to Moscow for talks with Mr Putin, Mr Johnson said he would “do everything possible for the diplomatic process”.
“I think it’s very important that we talk, but what we can’t do is end the sovereign rights of Ukrainians who want to join NATO,” he said.
Ms Truss defended her decision to hold talks with her Moscow counterpart Sergei Lavrov, insisting she had a clear message for Russia.
Talks between the foreign secretary and Mr Lavrov were strained last week, culminating in a bizarre press conference in which the Russian minister appeared to question his understanding of the crisis.
Ms Truss said: “I went to Russia to send a very clear message, that Russia is the aggressor. They have 100,000 troops on the Ukrainian border and if they invade Ukraine, the Russian people and the Russians. It will have a detrimental effect on the government.
“Of course, the Russians didn’t like what I said, but I still say it.
“And I want them to come back and I want them to know that the attack will come at a heavy price.”
Mr Lavrov described the meeting as a “conversation between the deaf and dumb” and claimed that Mr Truss had not heard Russia’s position and that Britain was not ready for such talks.
Armed Forces Minister James Happy said the British in Ukraine should not wait for tensions to rise before fleeing.
“This is a warning because within minutes of Putin’s order, missiles and bombs could land on Ukrainian cities, and this means that British citizens should leave now as long as they have the opportunity to do so.” Be present, “he told Sky News.
However, Downing Street insisted that British citizens should not expect “military aircraft” from Ukraine.
An official spokesman for the prime minister said: “British citizens should leave Ukraine by commercial means and there are still flights available.”
Labor leader Sir Kerr Starmer has said that if Russia invades Ukraine, parliament, which is not sitting this week, should be recalled.
He also called for tougher sanctions in response to “Russian aggression.”
“I would say that Russia wants to see its allies divided, it wants to see division in Britain, and we are not going to be divided and that is why we support the government that it is doing,” he said.
“We support the sovereignty of our allies and Ukraine, but yes, these sanctions must go further.”