His intervention comes as 7,000 more troops arrived on Ukraine’s border – a move Vladimir Putin insists is “purely defensive”.
The Prime Minister said: “There is still a chance to avoid unnecessary bloodshed, but it will require an overwhelming display of western solidarity beyond anything we have seen in recent history.
“Allies need to speak with one voice to stress to President Putin the high price he will pay for any further Russian invasion of Ukraine. Diplomacy can still prevail.
“That is the message I will take to Munich today as we redouble our efforts to prevent a grave miscalculation which would devastate Ukraine, Russia and the rest of Europe.”
In his speech, Mr Johnson will remind partners that, while there is still time to persuade Mr Putin to stand down Russian troops, the only prospect for this is if the western world speaks with one voice to dissuade and deter.
While in Munich, the Prime Minister will also meet a number of European partners to discuss the current response.
It comes after the Russian president denied he was going to invade Ukraine despite Moscow amassing more than 150,000 troops at the border.
Speaking at a news conference with Belarus president Alexander Lukashenko, Mr Putin said: "These military exercises, drills, are purely defensive and are not a threat to any other country.
"They were planned and all the objectives of these drills have been achieved."
Speaking through an interpreter, Mr Putin said they had discussed their demands for “security guarantees” from the West and claimed those requests had not been met.
He accused Ukrainian authorities of committing systematic human rights violations against the Russian-speaking population in the east of the country.
“We see also in Ukraine systematic violation of human rights and discrimination against the Russian-speaking population,” he said.
Mr Putin also called Western threats of sanctions a "violation of international law".
He said: “This sanction pressure first of all is completely illegitimate. It is a violation of international law. So these people only worry about international law when it suits them.
"We have lived in this paradigm for a number of years.
"They will impose sanction in any case, even if there are no reasons. They will find a reason.
"We are establishing our economic sovereignty. Even the allies of the United States are dealing with the consequences of the sanctions.”
The escalation also saw Kyiv mayor Vitali Klitschko call on Germany to provide Ukraine with "defensive weapons".
Addressing German foreign minister Annalena Baerbock, Mr Klitshcko said: "I want to say thank you very much for all friends who support Ukraine in this very difficult situation, who understand that without your support Ukraine cannot survive.
"We need, right now, defensive weapons.
"Thank you Germany for billions to rebuild infrastructure in Ukraine, but right now, in this critical situation, we [are] in front of one of the strongest armies in the world.
"Every aggressor who thinks to attack Ukraine has to understand that they have to pay a painful price.
"We are ready to fight. We are ready to defend our families, our state, our cities, our citizens. We need support.
"Thank you for 5,000 helmets, but it is not enough. We can't defend our country just with that."
The Netherlands plans to send military equipment to Ukraine, including rifles, ammunition, radar systems and mine-detecting robots.
Friday also saw the leader of rebel-held Donetsk, in eastern Ukraine, claim people will be evacuated to Russia.
Denis Pushilin, who is head of the self-proclaimed Donetsk People's Republic (DNR), announced on social media Russia had agreed to provide accommodation for people leaving.
Ukrainian foreign minister Dmytro Kuleba strongly denied "propaganda reports" the army was planning an offensive. US officials have said they believe rising violence in the Donbas region could form part of a Russian pretext to invade Ukraine.
Friday also saw Home Office minister Damian Hinds warn the West needs to be “steeled” to misinformation from the Kremlin following claims from US president Joe Biden and Mr Johnson that Russia intends to use a so-called “false flag” operation as a pretext for an invasion.
On Thursday morning, a kindergarten in the separatist-controlled Donbas region of Ukraine was shelled, with both Russian and Ukrainian governments claiming the other side was responsible.
Leaders from Nato states, including the Prime Minister, have said the incident was manufactured by the Russians to create grounds for war – a kind of disinformation campaign called a false flag operation.
Mr Biden said there was “every indication” that Russia continues to be prepared for war, despite claims the Kremlin was withdrawing troops from the border.
Mr Hinds said: “False flag is a form of disinformation. There are other forms of disinformation as well. The Putin regime is a global leader in the deployment of disinformation and wider information ops.”
The minister told Times Radio: “We need to be steeled to that. We need to understand what might be coming, what might be portrayed as some sort of spurious justification for an attack, for an invasion, and not take things at all at face value.”
Mr Hinds said an invasion of Ukraine was “not inevitable”, but could happen at “any time”, urging Russia to take a “diplomatic route”.
He said: “There are many, many troops built up on the Ukrainian border. There is no sign of that falling back, contrary to what has been claimed.
“Troops remain in place and there could be an invasion, there could be an incursion at any time, but it could also take longer.”