The US and UK leaders have said not all hope is lost for a diplomatic solution to the Ukraine crisis but warned the situation remained fragile.
In a 40-minute call, Joe Biden and Boris Johnson agreed a deal was still possible despite a chorus of warnings of imminent Russian military action.
On Monday, Russia’s foreign minister said diplomacy was “far from exhausted”.
As part of diplomatic efforts to ward off a possible invasion, Germany’s Chancellor Olaf Scholz is to meet Russia’s President Vladimir Putin later on Tuesday.
More than a dozen nations have urged their citizens to leave Ukraine, and the US has said aerial bombardments could begin “at any time”.
But in their conversation, Biden and Johnson said there remained a “crucial window” for diplomacy and for Russia to step back from its threats towards Ukraine, according to a Downing Street statement.
“The leaders emphasized that any further incursion into Ukraine would result in a protracted crisis for Russia, with far-reaching damage for both Russia and the world,” the statement added.