Boris Johnson said the UK has "provided further defensive military support to Ukraine"
Russian troops have not been welcomed into Ukraine but instead have faced “astonishing and tenacious resistance," the Prime Minister said.
“We as the international community have a responsibility to do everything we can to help the Ukrainians in their efforts,” he said.
“That is why the UK has trained 22,000 members of the Ukrainian armed forces and why we have provided further defensive military support to Ukraine.”
Boris Johnson said the UK and allies had put in place “the biggest package of sanctions ever imposed against a G20 nation”.
“We have seen organisations from banks to oil companies to football leagues to singing competitions who have made it clear that Vladimir Putin and his regime must be isolated from the international community for his actions,” he said at the Tapa military base in Estonia.
He also said: "We will not fight Russian forces in Ukraine.
UK troops on NATO's eastern flank will remain “firmly within the border of NATO members."
Estonia’s Prime Minister Kaja Kallas said Russia had gone from being a “difficult neighbour to a rogue state”.
At a joint press conference with Boris Johnson and NATO's Jens Stoltenberg, she also said Belarusian troops were also part of the invasion force in Ukraine.
“There’s no doubt Belarus is a co-aggressor in this conflict,” she said.