Boris Johnson warns Russia is on the 'edge of precipice' over Ukrainian invasion

Watch: Boris Johnson urges Putin to 'step back' from 'edge of precipice'

Boris Johnson has warned Russia could decide to invade Ukraine as early as Wednesday as he urged Vladimir Putin to "step back" from the "edge of a precipice".

The Russian President has amassed 130,000 troops on the borders of Ukraine and thousands more in the Black Sea, sparking fears bombs could begin to fall "minutes" after he gives the order to invade.

Johnson said on Monday the world needed to demonstrate the political and economic cost an invasion would have on Russia, including by ending reliance on its gas.

On a visit to Rosyth shipyard in Scotland, he said: “This is a very, very dangerous, difficult situation, we are on the edge of a precipice but there is still time for President Putin to step back.”

He called for more dialogue and urged Russia to avoid a “disastrous” invasion.

Reports based on US intelligence assessments have suggested an invasion could be launched as soon as Wednesday.

On Monday a defence minister warned the continent of Europe is closer to war than it has been for the past 70 years, a defence minister has warned, as he urged British nationals to flee Ukraine while they still can.

James Heappey told BBC Radio 4 Today: "All of the combat enablers are in place and my fear is that if all of this was just about a show to win leverage in diplomacy that doesn’t require the logistics, the fuel, the medical supplies, the bridging assets, the unglamorous stuff that actually makes an invasion force credible, but doesn’t attract headlines. Yet all of that is now in place too.

“That’s why there’s real urgency to the diplomatic negotiations that continue. That is why this is a very serious time for the whole world, really, to come together and to send a message to Russia that this is behaviour that will not be accepted and that we stand behind Ukraine, and that the financial sanctions if he were to cross the border would be absolutely profound.”

Heappey told Sky News that the UK is hoping Russia is amassing forces for the purpose of "diplomatic leverage" but there is now a "very credible force".

Read more: With Russian troops poised on the border with Ukraine, 'information warfare' has already begun

"My nervousness is if this was just a play by Vladimir Putin, he had that [diplomatic leverage] when he had 50,000 troops on the border of Ukraine but he's kept on building that up," the armed forces minister said.

He warned his "fear" is that an invasion is "now very imminent", although that does not mean an attack is definitely going to happen.

However, he said there are diplomatic tools that could be used to prevent an attack.

There are currently an unknown number of Britons in Ukraine, with the Foreign Office urging them to leave as soon as possible.

Heappey said a website has been used to keep people in touch with the Foreign Office, but said "we are beyond the time now where I am advising people to register on a website".

He added: "I'm being very, very clear with people that they should leave Ukraine now whilst there are the commercial means to do so and whilst the motorways are available for them to drive out over the border.

"This isn’t a warning about something that could happen in three months’ time, this isn’t a warning that will be followed by further warnings because greater imminence has been reached.

Read more: Ominous Russian movements in Black Sea raise alarm

"This is a warning because minutes after Putin gives the order, missiles and bombs could be landing on Ukrainian cities, and that means British citizens should leave now whilst they have the opportunities to do so."

Heappey warned that the attack could happen with "no notice"

He said: “Russia has concentrated artillery missile systems and combat air in the area. And, perhaps more ominously, although it grabs less headlines, all of the combat enablers, the logistics, the fuel, the medical supplies, the bridging assets, are all also now in place.

“So, the reason that the travel advice changed on Friday and the urgency of the messaging since is that the attack could effectively now happen with no notice.”

Watch: Ukraine ambassador - Ukraine could drop Nato ambitions to avoid war

It comes as Ukraine’s ambassador to the UK said the country could consider dropping its ambition to join Nato to avoid war.

Vadym Prystaiko told BBC Radio 5 that the country, which he said was being threatened and blackmailed, would consider “serious concessions” including removing the goal of joining the Nato alliance from the Ukrainian constitution.

On Thursday, the Nato secretary-general warned Europe "must prepare for the worst" amid the rising tensions.

Prime minister Boris Johnson met Jens Stoltenberg in Brussels on Thursday amid heightened tensions in Ukraine, after Putin called his country "one of the leading nuclear states".

He warned Europe not to get involved in any potential fight, saying: "There will be no winners, and you will be pulled into this conflict against your will."