Boris Johnson called in City chiefs to No10 to press them to ensure a “hardcore” implementation of sanctions announced by Britain on Tuesday.
The Prime Minister was also expected to announce that the UK is sending more military hardware to Ukraine, having already despatched 2,000 anti-tank missile launchers.
A Whitehall source told the Standard: “It’s a case of help protect Ukraine and punish the pariah.”
However, the Government faced calls from senior MPs to impose tougher and unexpected new sanctions to hit the Kremlin or risk being “two steps behind in the diplomatic chess game”.
The City chiefs, who include regulators and major financial institutions, were expected to receive a security briefing, including on the situation on the ground in Ukraine, at their meeting in Downing Street this afternoon.
Up to 190,000 Russian military personnel are believed to be surrounding Ukraine, with thousands having been moved into position ready for an attack, according to Western sources.
Early Wednesday morning, Australian PM Scott Morrison said a full-scale invasion was “likely” within the next 24 hours.
Ukraine’s top security official Oleksiy Danilov said Ukraine would impose a state of emergency on all its territory, apart from the Donetsk and Luhansk regions, parts of which were seized by Moscow-backed separatists in 2014.
But there was confusion over whether Russian troops had yet entered the two breakaway “republics” of Donetsk and Luhansk with Foreign Secretary Liz Truss saying: “We are seeing all the precursor to invasion.
Pressed on LBC on whether a Russian so-called “peacekeeping force” had been deployed, she added: “Putin has said they were going to be deployed. We do not have verified evidence that that has taken place yet.”
In other developments on Wednesday:
Mr Putin trumpeted the growing “combat potential of our armed forces” including further developing hypersonic weapons and more use of advanced digital technologies and artificial intelligence.
As Russia marked “Defender of the Fatherland Day” honouring its troops, the Kremlin put out a video of the president saying a diplomatic solution to the crisis was possible but that the interests of Russia and the security of its citizens are “non-negotiable”.
Reports suggested more Russian forces had entered the Donbas region at the centre of the crisis.
The Ukrainian military said on Wednesday one soldier had been killed and six wounded in shelling by pro-Russian separatists in east Ukraine in the past 24 hours as ceasefire violations remained high.
A fresh image showed a Russian field hospital in Belgorod region, close to the Ukrainian border, with the US warning that blood banks are in position near the frontier.
The UK said it was ready to guarantee up to $500 million in loans to support Ukraine and mitigate the economic effects of Russian aggression.
Mr Johnson was expected to correct the parliamentary record over wrong comments yesterday that Chelsea’s Russian owner Roman Abramovich had been sanctioned by the UK.
Ukraine urged its citizens living in Russia to leave immediately.
In an effort to deter Mr Putin, Ms Truss vowed to inflict pain on the Russian regime following its decision to order troops into the separatist held areas of eastern Ukraine. She said the UK and its western allies will escalate sanctions if the Kremlin goes further.
But senior Tories joined opposition MPs in criticising the Government for pulling its punches on sanctions against Russia.
Jeremy Hunt, a former foreign secretary, said Britain needed to go further: “What we have to remember is that Putin has both predicted these sanctions, and indeed further sanctions, and discounted them.
“If we are going to avoid being two steps behind in the diplomatic chess game, we have to do some things that he’s not expecting.”
And Tom Tugendhat, Conservative chairman of the Commons foreign affairs committee, said: “Deterrence only works if your adversary thinks you are serious. That’s why the Army always says ‘clout don’t dribble’.”
Shadow foreign secretary David Lammy said the Government needs to act now. “I think the mood of the entire House of Commons yesterday was that the Government were not being strong enough,” he told BBC Breakfast.
In his announcement to the Commons, the Prime Minister said five Russian banks and three oligarchs would be targeted with their UK assets immediately frozen and British individuals and entities barred from having dealings with them.
The three billionaires, Boris and Igor Rotenberg and Gennady Timchenko, who all have close links to the Putin regime, were also banned from travelling to the UK.