French President Emmanuel Macron has said the coming days will be crucial to de-escalating the Ukraine standoff, after a meeting with Russia’s Vladimir Putin.
Mr Putin hinted that progress had been made during his first Moscow summit with a Western leader since Russian troops massed on Ukraine’s borders.
Moscow has denied any plans to invade.
However, Western powers have become increasingly concerned by the possibility of a conflict.
US officials said on Sunday that Russia has assembled 70% of military forces needed for a full-scale invasion.
On Monday, President Joe Biden threatened to shut down a key Russian gas pipeline to Germany if Moscow invades Ukraine following a meeting with German Chancellor Olaf Scholz in Washington.
British Prime Minister Boris Johnson has also indicated his support for sanctions. Writing in The Times newspaper on Tuesday, he added that the UK is considering deploying Royal Air Force (RAF) fighters and Royal Navy warships to the region.
Western countries have already rejected a number of Moscow’s demands, including that the Nato defence alliance rule out Ukraine becoming a member, and that it reduce its military presence in eastern Europe.
They have instead suggested other areas of negotiation, for example talks on cutting back nuclear weaponry.
Mr Macron, who spoke with Mr Putin over a five-hour dinner which included reindeer with sweet potatoes and blackberries, told reporters the coming days would be “decisive” and “require intensive discussions which we will pursue together”.
The Russian president said that some of Mr Macron’s proposals “could form the basis of further joint steps”, stating that they were “probably still too early to talk about”.
The pair will speak again after the French president travels to Kyiv on Tuesday to meet Ukrainian President Volodymyr Zelensky.
Mr Putin later repeated earlier warnings that should Ukraine joins the Western military alliance Nato and attempt to take back Crimea – which Russia annexed eight years ago – by force, Europe could get sucked into a major conflict.
“Do you want France to fight with Russia?” he asked French reporters. “That’s what will happen. And there will be no winners.”
In Washington, Chancellor Scholz told reporters it was important for “Russia to understand that a lot more could happen than they’ve perhaps calculated with themselves”, according to news agency AP.
Mr Scholz – on his first trip to Washington since becoming chancellor and under criticism for his response to the Ukraine crisis – added that the US and Germany were “absolutely united” on sanctions against Russia should it invade Ukraine, saying “we will do the same steps and they will be very, very hard to Russia”.
However, he was more ambiguous about Nord Stream 2 than US President Biden, who said the US “will bring an end” to the controversial pipeline – which will double Moscow’s gas exports to Germany – “if Russia invades”.
Mr Biden did not give specifics, responding to a question about how he would do this by saying: “I promise you we will be able to do it.”
The 1,225km (760-mile) Nord Stream 2 pipeline took five years to build and cost $11bn (£8bn), but as yet has not started operating, after regulators said in November it does not comply with German law and suspended its approval.