Joe Biden prepares for meeting with Vladimir Putin as Russian forces continue to mass at Ukraine border

Fears of an invasion in one of Europe’s most unstable regions are growing, as two world leaders prepare for a “high stakes” meeting.

Joe Biden has held a call with European Union leaders ahead of sure-to-be tense talks with Russia’s Vladimir Putin tomorrow, as the situation on the border between Russia and Ukraine grows ever more serious.

Last week, Mr Putin warned NATO nations they would be crossing a “red line” if they were to deploy troops into areas of concern, as an estimated 94,000 Russian troops mobilised near the border.

According to Sky News UK, Mr Biden, British Prime Minister Boris Johnson, French President Emmanuel Macron, outgoing German Chancellor Angela Merkel and Italy’s Mario Draghi all “shared concern about the Russian military build-up on Ukraine’s borders and Russia’s increasingly harsh rhetoric” in talks this week.

“What I am doing is putting together what I believe will be the most comprehensive and meaningful set of initiatives to make it very, very difficult for Mr Putin to go ahead and do what people are worried he may do,” Mr Biden told reporters, alluding to the threat of a Russian invasion.

A spokesman for Mr Johnson said the cohort of Western leaders “emphasised the need to provide a united front in the face of Russian threats and hostility”.

"The leaders called on Russia to de-escalate tensions and reaffirmed their staunch support for Ukraine’s territorial integrity,” the spokesman said.

Mr Biden and Mr Putin will converse tomorrow on the issue, after last trading words in June at a summit in Geneva. Mr Biden is expected to warn Russia not to invade.

“Our objective here is conveying diplomatically that this is the moment for Russia to pull back their military build-up at the border, that diplomacy is the right path forward,” White House Press Secretary Jen Psaki told reporters today.

Mr Putin will reportedly press for a binding commitment that Ukraine will not join NATO. Today his spokesman dismissed fears of a Russian invasion as “aggressive and hostile rhetoric” from western powers.

Biden met his Russian counterpart for the first time as President in Geneva in June. Now, as words between Putin and NATO heat up, experts believe the stakes between the superpowers have never been higher.

Russia has mobilised nearly 100,000 troops, including conscripts, near the Ukrainian border.

According to Mark Stone, Sky News UK’s US Correspondent based in Washington, tomorrow’s video call with Mr Putin “is the trickiest diplomatic conversation of Joe Biden‘s presidency” so far.

“Geneva now feels a long time ago. Today‘s stakes are high,” Mr Stone said.

NATO leaders have co-ordinated a message for the Russian state, threatening tough sanctions against the superpower should it proceed with anything rash in the region.

Meanwhile, Russia has strongly opposed the idea of Ukraine becoming a NATO nation.

“So is Russia really about to invade Ukraine? White House officials seem genuinely unsure,” Mr Stone continued.

“For weeks, American intelligence has suggested an imminent Russian invasion of Ukraine.”

On Monday, US time, the Wall Street Journal quoted CIA Director William Burns as saying intelligence agencies had observed a “steady and unusual build-up” of Russian forces.

“I would never underestimate President Putin’s risk appetite on Ukraine,” Mr Burns said at a summit hosted by the newspaper.

“We don’t know that Putin has made up his mind to use force. But what we do know is that he’s putting the Russian military, Russian security services in a space where they could act in a very sweeping way.

“He may see this (northern hemisphere) winter, tactically, as kind of offering a favourable landscape.”

Over 8,000 servicemen and about 350 items of military hardware and weaponry recently took part in an amphibious landing drill in Crimea.

NATO Secretary-General Jens Stoltenberg said this week Russia had “no right” to demand Ukraine be permanently excluded from the alliance.

“It’s Ukraine and 30 NATO allies that decide when Ukraine is ready to join NATO,” he said.

“Russia has no veto, Russia has no say and Russia has no right to establish a sphere of influence, trying to control their neighbours. This idea that NATO’s support to sovereign nations is a provocation is just wrong.”

Russian Foreign Minister Sergey Lavrov, who last week met with US Secretary of State Antony Blinken in Sweden has also vaguely warned of retaliation should sanctions be imposed on his government.

“If the new ‘sanctions from hell’ come, we will respond,” Mr Lavrov said.

“We can‘t fail to respond.”