"GRIM" intelligence shows Russia's aggression against Ukraine is reaching its "most dangerous" moment yet, Boris Johnson warned today.
At a press conference at Nato HQ in Brussels the PM warned Vladimir Putin to step back from the edge of war in Ukraine - or pay the price.
The sabre-rattling Kremlin strongman is ramping up menacing military drills on the border.
In a sobering address Mr Johnson said: "It's possible that something absolutely disastrous could happen very soon indeed - and our intelligence, I'm afraid to say, remains grim.
"This is probably the most dangerous moment I would say - in the course of the next few days - in what is the biggest security crisis that Europe has faced for decades."
He added "we must resist, we must oppose any return to the days when the fates of nations are decided over their heads by a handful of great powers."
Mr Johnson has vowed to send 1,000 more troops to the frontline and will personally visit British soldiers in Poland following his TV address.
He is imploring the Kremlin to keep diplomatic options alive to avoid "the blood-soaked tragedy of another Russian invasion of Ukraine".
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The PM travelled on from Brussels to Warsaw this afternoon where he held a joint press conference with its leader Mateusz Morawiecki.
Boris said the UK and Poland were "standing shoulder to shoulder" to face down Russian aggression.
He added: "The lesson of the last 100 years is that when Poland is threatened then we are all threatened and we are all affected."
The PM added he would "tirelessly pursue the path of diplomacy" to end the crisis and urged the Kremlin to "de-escalate and disengage".
Mr Morawiecki praised the UK for its support after the number of British troops stationed in Poland was bolstered to 500.
He said Boris was one of the few world leaders not caught "napping" by Russian aggression.
The Polish PM said: "Many European leaders have suddenly been woken up from their geopolitical nap.
"We were not napping, not myself and Boris, we were aware of the fact that there are threats which are very, very apparent.
"So now the rest of the world needs to wake up."
Mr Morawiecki also criticised Germany's reluctance to sever its energy links to Moscow if there's an invasion.
He added: "As regards Nord Stream 2, I would like to appeal to our German allies.
"You have to announce, as soon as possible, that this gas pipeline should not be used as blackmail."
TROOPS ON STANDBY
Earlier a hopeful Mr Johnson wrote in the Wall Street Journal: "If we combine strong deterrence with patient diplomacy, I believe we can find our way through this crisis."
And throwing a protective arm around Ukraine, he added: "We are not going to conclude a grand bargain heedless of our allies in central Europe.
"We are not going to treat the nations at the heart of our Continent as pawns on a chessboard to be haggled over or sacrificed.
"Every independent state, including Ukraine, has a sovereign right to decide its own foreign policy and seek its own alliances."
He has sent Liz Truss to Moscow to stress to her Russian counterpart that an attack would trigger Western nations to impose crippling sanctions.
She is the first foreign secretary to visit the Russian capital in more than four years.
Ukraine has already warned it is prepared to fight to the death to protect its homeland.
And this morning Defence Secretary Ben Wallace made clear a Russian invasion is a "lose-lose" scenario.
He told Times Radio: "No one is going to win from an aggressive invasion of a sovereign state."
Our soldiers will be put on standby to help support a “humanitarian response” if Russia pushes ahead with plans for a bloody war in Ukraine.
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Defence chiefs have seen “no signs” of any Russian de-escalation.
The longer the mass of troops are there, the more they fear they will get used.