Neither side pulled any punches, with US Secretary of State John Kerry saying what happens in Ukraine is crucial for Europe's future while his Russian counterpart Sergei Lavrov blasted wilful and two-faced Western interference.
"Nowhere is the fight for a democratic, European future more important today than in Ukraine," Kerry told political, diplomatic and military leaders at the Munich Security Conference.
"The United States and EU stand with the people of Ukraine in that fight," said Kerry who was due later Saturday to meet Ukrainian opposition leaders including former world boxing champion Vitali Klitschko in Munich.
Mr Kerry, speaking with US Defence Secretary Chuck Hagel alongside, said the "vast majority of Ukrainians want to live freely in a safe, prosperous country".
"They are fighting for the right to associate with partners who will help them realise their aspirations -- and they have decided that means their futures do not have to lie with one country alone, and certainly not coerced."
Earlier Saturday, the party of opposition leader Arseniy Yatsenyuk said he had warned European officials it was "very likely" Kiev would "resort to a use of force scenario, including with the involvement of the Ukranian army".
The Ukrainian Defence Ministry, which previously said it would not interfere in the crisis, warned also that protesters' seizure of government buildings was unacceptable and that "further escalation of the confrontation threatens the country's territorial integrity".
European Council President Herman Van Rompuy told another panel that the EU wanted good relations with Russia, that it was an essential element in Europe's peace and prosperity but that the Ukrainian people had to have the right to choose their own future, a future with Europe.
The West and Russia have been at loggerheads over Ukraine since President Viktor Yanukovych ditched an EU association accord in November under pressure from a Moscow trying to bring its former Soviet satellite back into the fold.
Mr Yanukovych's decision sparked massive anti-government rallies, which turned increasingly violent last month after he rushed through a series of curbs on protests.
The move prompted an escalation of the violence on the streets and the president then cancelled them and accepted the resignation of the government.
Mr Kerry's planned meeting with Ukraine opposition may have explained the unequivocally harsh remarks by Mr Lavrov who accused the West of stoking the violence in Kiev in a clear example of double standards.
"Why are many prominent EU politicians actually encouraging such actions although back home they are quick to severely punish any violations of the law?" Mr Lavrov told the conference.
"What does incitement of increasingly violent street protests have to do with promoting democracy?" he asked, speaking at the same panel as Mr Van Rompuy.
"Why don't we hear condemnation of those who seize and hold government buildings, attack the police, torture police, use racist and anti-Semitic and Nazi slogans?" Mr Lavrov said.
EU foreign affairs head Catherine Ashton is due to visit Kiev again next week, having previously met the government and opposition figures several times there to call for peaceful dialogue.
Other prominent EU, US and international figures have also been frequent visitors to Kiev, drawing a strong government and Russian response although Mr Lavrov's remarks Saturday were unusually blunt in comparison.
Describing the situation in Ukraine as raising "fundamental questions" about EU-Russia relations, he said that in this case "a choice is being imposed."
Europe's future should "not be about new spheres of influence... it should be about how all countries" cooperate in the interest of all, he said.
For his part, Mr Kerry said "Russia and other countries should not view the European integration of their neighbours as a zero-sum game".
"The lesson of the last half-century is that we can accomplish much more when the United States, Russia and Europe work together," he added.