With war clouds gathering over Ukraine, international diplomacy goes into overdrive on February 7 with the French and Russian presidents to talk in Moscow and the German chancellor heading to the White House to meet with US leader Joe Biden.

Also on February 7, the German, Czech, Slovak and Austrian foreign ministers were expected in Kyiv, which has played down dire US warnings that Moscow had stepped up preparations for a major incursion into Ukraine.

US officials have said the Kremlin has assembled 110,000 troops along the border with its pro-Western neighbour but intelligence assessments have not determined whether President Vladimir Putin has actually decided to invade.

They said Russia is on track to amass a large enough force – some 150,000 soldiers – for a full-scale invasion by mid-February.

Such a force would be capable of taking the capital Kyiv in a matter of 48 hours in an onslaught that would kill up to 50,000 civilians, 25,000 Ukrainian soldiers and 10,000 Russian troops and trigger a refugee flood of up to five million people, mainly into Poland, the officials added.

On top of the potential human cost, Ukraine fears further damage to its already struggling economy.

And if Moscow attacks Ukraine it could face retaliation over the Nord Stream 2 pipeline – set to double natural gas supplies from Russia to Germany – with Berlin threatening to block it.

Russia is seeking a guarantee from NATO that Ukraine will not enter the alliance and wants the bloc to withdraw forces from member states in eastern Europe.

Moscow denies that it is planning to invade Ukraine, and Kyiv’s presidency advisor said the chances of a diplomatic solution to the crisis remained “substantially higher than the threat of further escalation”.

On Twitter, Ukraine’s Foreign Minister Dmytro Kuleba sought to calm tensions, saying: “Do not believe the apocalyptic predictions. Different capitals have different scenarios, but Ukraine is ready for any development.”

President Emmanuel Macron of France, which currently holds the rotating presidency of the EU, will be in Moscow on February 7 and Kyiv on February 8 to spearhead efforts to de-escalate the crisis.

He is expected to push forward a stalled peace plan for the festering conflict with Russian-backed separatists in eastern Ukraine.

The trip will be a political gamble for Macron, who faces a re-election challenge in April.

Also on February 7, German Chancellor Olaf Scholz will meet with Biden in Washington.

“We worked hard to send a clear message to Russia that it will have a high price if they were to intervene into Ukraine,” Scholz told the Washington Post in an interview ahead of his meeting.

“I really appreciate what President Biden is doing in the bilateral talks between the US and Russia. They are very difficult.”

Biden has reacted to the Russian troop buildup by offering 3,000 US forces to bolster NATO’s eastern flank, with a batch of the troops promised arriving in Poland on February 6.

But US National Security Advisor Jake Sullivan told Fox News February 6 that Biden “is not sending forces to start a war or fight a war with Russia in Ukraine”.