Western powers have called on Russia to lower tensions with Ukraine, ahead of a video call between US President Joe Biden and Russia’s Vladimir Putin.
Responding to fears of a Russian invasion, Mr Biden agreed with leaders of the UK, France, Germany and Italy to use “all the tools at their disposal”.
Moscow denies it has plans to attack.
But Russia has moved thousands of troops near Ukraine’s eastern borders, and Ukraine says tanks have been moved to the front line inside its territory.
Hours before the video talks scheduled for 15:00 GMT, it appeared Washington was not planning a US military response, but focusing instead on tough economic sanctions.
In a conference call on Monday night, the White House said the five Western leaders had formed a joint strategy “to impose significant and severe harm on the Russian economy” should Russia launch an invasion.
They “reaffirmed their staunch support for Ukraine’s territorial integrity”, Downing Street said.
Possible measures include restrictions on Russia’s banks converting roubles into foreign currencies, or even disconnecting Russia from the Swift global financial payment system, reports say.