Prime Minister Boris Johnson delivered a stark warning to President Vladimir Putin yesterday of “significant consequences” if his troops invade Ukraine.
He told Putin of his “deep concern over the build-up of Russian forces on Ukraine’s border,” amid fears 175,000 of Moscow’s combat troops are preparing for a deeper conflict.
The Russian President was told further destabilising action by Moscow would be a "strategic mistake," with claims an invasion could be imminent.
A No 10 spokesman said: “He expressed the United Kingdom’s deep concern over the build-up of Russian forces on Ukraine’s border, and reiterated the importance of working through diplomatic channels to de-escalate....
“The Prime Minister emphasised the UK’s commitment to Ukraine’s territorial integrity and sovereignty, and warned that any destabilising action would be a strategic mistake that would have significant consequences.”

On Sunday, G7 foreign ministers warned Moscow against breaking international law with an incursion further into Ukraine territory.
Thousands of Ukrainian troops are on high-alert for a Russian invasion with as many as 175,000 of Moscow’s forces close to the border.
Western intelligence believe pro-Moscow separatists are also preparing for conflict, spurred on by Moscow’s GRU military intelligence spooks.
Around 14,000 people have been killed along the Ukraine-Russia border in fierce fighting since Moscow invaded the Ukraine territory of Crimea in 2014.

Crimea remains internationally part of Ukraine, despite Moscow’s forced annexation of the region.
It is believed President Putin’s commanders have ordered up fresh artillery units and tanks to the frontline, with 50 tactical battle groups and more than 100 combat battalions.
Worryingly Moscow’s commanders are also thought to have drafted in field hospitals closer to the border.
Ukraine’s Foreign Minister recently warned: “There will be many dead Russian soldiers,” if Putin orders an invasion.
The Mirror understands western, including UK special forces, may be positioned in airfields throughout Ukraine as advisers, should war break out.
The United States has also beefed up Ukraine’s defences with multi-million pound packages of fresh ammunition and artillery supplies.
Hundreds of British Paras last year jumped into Ukraine with local airborne forces, as if practising for a Russian invasion.
They included the SAS - style, elite Pathfinders, who are tasked to ghost behind enemy lines by parachute and call in more elite Paras for the main battle.