Britain is not ruling out sanctions targeted at Kremlin chief Vladimir Putin in person if Russia invades Ukraine, Foreign Secretary Liz Truss says.
United States President Joe Biden said he would consider personal sanctions on Mr Putin if Russia invades Ukraine, as Western leaders stepped up military preparations and made plans to shield Europe from a potential energy supply shock.
Russia has massed more than 100,000 troops around Ukraine and the West fears it may invade in an attempt to annex its former Soviet republic.
Ms Truss said on Wednesday that Britain was already supplying support to Ukraine.
British Foreign Secretary Liz Truss. Source: AAP
"We're supplying defensive weapons. We're providing economic support," she told Sky on Wednesday.
"We are urging Russia to desist from an incursion and we're making it very clear that if they were to do that there would be severe economic cost to Russia - severe sanctions."
Asked about possible sanctions on Mr Putin, Ms Truss said: "We're not ruling anything out.
"We'll be bringing forward new legislation to make our sanctions regime tougher so we are able to target more companies and individuals in Russia. We will be bringing that forward in the next few days. I'm not ruling that out."
Russia has repeatedly said it has no intention of invading Ukraine, that it can deploy troops wherever it wants on its own territory and that the West is gripped by Russophobia.
Joe Biden 'would see' sanctions imposed on Vladimir Putin
US President Joe Biden said he will consider personal sanctions on President Vladimir Putin if Russia invades Ukraine, as Western leaders stepped up military preparations.
The rare sanctions threat came as NATO placed forces on standby and reinforces eastern Europe with more ships and fighter jets in response to Russia's troop build-up near its border with Ukraine.
Russia denies planning an attack and said the crisis is being driven by NATO and US actions.
It is demanding security guarantees from the West, including a promise by NATO never to admit Ukraine, as Moscow sees the former Soviet republic as a buffer between Russia and NATO countries.
Russia's present demands are based on Mr Putin's long sense of grievance and his rejection of Ukraine and Belarus as truly separate, sovereign countries. Source: AP
Following multiple rounds of US-Russia talks that failed to reach a breakthrough, Mr Biden - who has long warned Moscow of economic consequences - upped the ante on Tuesday by saying Mr Putin could personally face sanctions.
He told reporters that if Russia were to move into Ukraine with the estimated 100,000 soldiers it has massed near the border, it would be the "largest invasion since World War II" and would "change the world".
Asked if he would see himself imposing sanctions on Mr Putin directly if Russia invaded Ukraine, Mr Biden responded: "Yes. I would see that."
Direct US sanctions on foreign leaders are rare but not unprecedented. Others who have faced sanctions include Venezuela's Nicolas Maduro, Syria's Bashar al-Assad and Libya's Muammar Gaddafi.
Meanwhile, Russia's ambassador in Australia said the country's decision to withdraw diplomatic staff from its embassy in Ukraine "would be funny if it wasn't so sad".
Aleksey Pavlovsky has talked down fears of an invasion of Ukraine, saying there is no intention to go to war as 100,000 troops amass on the border.
"We should use our critical thinking. Isn't it a funny way to prepare an invasion by just gathering troops on the border and let them sit there for months," he told the ABC.
"When you prepare an invasion you just do it promptly. These troops are not a threat, they are a warning to Ukraine's rulers not to attempt any reckless military adventures."
The Russian ambassador also criticised Australia's decision to issue a Do Not Travel declaration for Ukraine and for its call for citizens in the country to leave.
"(The) decision was a strange one. You can't help wondering why when all but four diplomatic missions in Kyiv keep working normally," he said.
Mr Pavlovsky also talked down the impact of sanctions, which have been threatened by western nations including Australia, saying they don't work.
"The position of Australia on this is regrettable," he said.