BERLIN: Russia said Thursday it would hold huge naval drills across four seas, in a new bout of sabre-rattling as tensions with the West soared to new heights over the threat that Moscow would march on Ukraine.

The Russian defence ministry’s announcement to deploy more than 140 warships and supporting vessels this month and in February to the Atlantic, Pacific, Arctic and Mediterranean followed an angry condemnation from the Kremlin of what it described as “destabilising” remarks from US President Joe Biden.

The American leader had vowed a “severe” response to any invasion of Ukraine, as he assessed that Russian President Vladimir Putin will “move in” on the ex-Soviet nation.

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

In a bid to defuse the worst tensions between Russia and the West in decades, US Secretary of State Antony Blinken is on a whirlwind diplomatic tour that took him to Berlin on Thursday.

Blinken is huddling with his counterparts from France and Germany, as well as Britain’s junior foreign minister, seeking a common front against Moscow, a day before his crunch talks with Russia’s Sergei Lavrov.

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”.

Upping the ante, Russia announced new war games on the seas involving “more than 140 warships and support vessels, more than 60 aircraft, 1,000 pieces of military equipment, and about 10,000 servicemen”.

They follow joint military drills Wednesday between Russian forces and those of ex-Soviet republic Belarus, which also neighbours Ukraine. A US official said the exercises could presage a permanent Russian military presence involving both conventional and nuclear forces in Belarus.

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

Hours before Blinken arrived in Berlin to coordinate the possible response to Russia, Biden sparked controversy as he appeared to indicate that a “minor incursion” might prompt a smaller reaction from NATO allies.

“It’s one thing if it’s a minor incursion, and then we end up having a fight about what to do and not do, etcetera,” he said.

But the White House moved swiftly to clarify the comments, with Press Secretary Jen Psaki vowing any Russian movement in Ukraine would face “severe” retaliation.

Statements like that, said Kremlin spokesman Dmitry Peskov, “can facilitate the destabilisation of the situation because they can inspire some hotheads in Ukraine with false hopes”.

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.

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.

But in Kyiv on Wednesday, Blinken said he would not present such a formal response at Friday’s talks with Lavrov in Geneva. Rather, the onus is on Putin to dispel fears that Moscow is planning an invasion of its pro-Western neighbour.

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