As tensions between Russia and the West continue over the Ukraine crisis, United States Secretary of State Antony Blinken warned Thursday that Russia risked reviving Europe's dangerous Cold War era of division.

Speaking in Berlin a day before talks with Russian Foreign Minister Sergei Lavrov, Blinken said that by demanding that Ukraine not enter NATO, Russia was violating the principle that nations can make their own decisions.

"To allow Russia to violate those principles with impunity would drag us all back to a much more dangerous and unstable time, when this continent, and this city, were divided in two... with the threat of all-out war hanging over everyone's heads," he said.

"It would also send a message to others around the world that these principles are expendable," he said.

"It's bigger than a conflict between two countries, and it's bigger than a clash between Russia and NATO. It's a crisis with global consequences. And it requires global attention and action."

Blinken warned of devastating destruction from an invasion, following eight years of a pro-Russian insurgency in eastern Ukraine that has claimed more than 13,000 lives.

"The human toll of renewed aggression by Russia would be many magnitudes higher than what we've seen to date," he said.

With tens of thousands of Russian troops massed on the Ukrainian border, fears are mounting that a major conflict could break out in Europe.

Moscow insists it has no plans to invade but has at the same time laid down a series of demands – including a ban on Ukraine joining NATO – in exchange for de-escalation.

Washington has rejected Moscow's demands as "non-starters" and NATO chief Jens Stoltenberg this week insisted that the alliance "will not compromise on core principles such as the right for each nation to choose its own path."

The West has repeatedly warned Russia it would pay a "high price" of economic and political sanctions should it invade Ukraine.

With both sides' positions entrenched, a series of talks between Western and Russian officials in Geneva, Brussels and Vienna has failed to yield any breakthrough.

Dialogue preferred

NATO allies have signalled their willingness to keep talking but Moscow has demanded a written response on its proposals for security guarantees.

On the Russian wish list are measures that would limit military activities in the former Warsaw Pact and ex-Soviet countries that joined NATO after the Cold War.

Ukraine has been fighting Moscow-backed forces in two breakaway eastern regions since 2014, when Russia annexed the Crimean peninsula from Ukraine.

More than 13,000 people have been killed, and the latest Russian troop build-up has also greatly rattled neighbors in the Baltics.