Boris Johnson today vowed to target Vladimir Putin's gold reserves, saying the "red line has already been crossed" of war crimes in Ukraine.
The Prime Minister said there is now 'no question' Russia has committed war crimes and its President should be prosecuted in the International Criminal Court as he jetted for talks with NATO leaders.
He also said it was "beyond satire" that "bonkers" UEFA could give Russia the Euro 2028 tournament.
Mr Johnson spoke just before boarding a flight to NATO's Brussels HQ, where world leaders including US President Joe Biden will discuss the growing threat of chemical and biological weapons.
Last night he said Britain is sending another 6,000 missiles to Ukraine as its forces battle Vladimir Putin ’s invaders.
Today he warned the UK could target the Russian president's gold reserves in response to the invasion of Ukraine.
He told LBC: "We need to do more, and so we need to do more economically. Can we do more to stop him using his gold reserves, for instance, in addition to his cash reserves?
"What can we do more to sanction Swift? And then we need to do more to give the Ukrainians military support."
Ahead of President Joe Biden's attendance at the summit, the US administration announced it had formally assessed that Russian forces had committed war crimes in Ukraine.
Secretary of state Antony Blinken cited the besieged city of Mariupol where an estimated 100,000 people remain trapped with chronic shortages of food and clean drinking water.
Boris Johnson today warned Russian president Vladimir Putin had already crossed a "red line" with his "barbarism" towards Ukraine, and said he should be tried in the International Criminal Court.
“There’s no question that what they are doing are war crimes," the Prime Minister told LBC.
“And we must make sure we steadily collate all the evidence about the use of thermobaric weapons, the deliberate targeting of civilians - everything we need to eventually bring prosecutions.”
He added: "We all want to see some solution in Ukraine. Everybody is hoping that Putin will pull back and stop this incredible barbaric slaughter that he's engaged on.
"But the only way to do that - we think there's a huge amount of unity - is to keep going with the pressure that we've applied, and to increase it.
"And the point I'm going to make today is look, you know, he's already crossed a threshold of barbarism in the way he's behaving. People talk about new red lines for chemical, biological, tactical nuclear weapons or whatever. For me, the red line already has been crossed.
"He's bombing indiscriminately civilian centres. He's causing huge numbers of casualties in wholly innocent populations."
The NATO meeting, which will be addressed remotely by Ukraine's President Zelensky, is expected to sign off on the formation of four new battlegroups in eastern Europe.
Nato secretary general Jens Stoltenberg said the battlegroups - each numbering between 1,000 and 1,500 troops - would be deployed in Hungary, Slovakia, Romania and Bulgaria.
The alliance already has 40,000 troops in Europe under its direct command, nearly 10 times the number it had a few months ago.
Mr Stoltenberg told a news conference on Wednesday that the forces will remain in place "as long as necessary".
"This is a significant reinforcement of our presence in the east with air, sea and land forces," he said.
"We are there to protect and defend allies, ready to respond massively to any potential threat or attack against any Nato allied country."
Mr Johnson also compared Ukrainian president Volodymyr Zelensky to former prime minister Winston Churchill, praising him for giving the Ukrainian people their "roar".
He told LBC: "I think that President Zelensky has proved to be a quite remarkable leader of his people - he's rallied them and he's been their voice.
"He knows, as Churchill said of himself, he may not have been the lion but he's been privileged to give the roar.
"It's the Ukrainian people who have been the lion, and he's expressed their will and their sense of defiance."
