President Vladimir Putin launched an invasion in part to stop Nato gaining an extra member - Ukraine. Instead Nato is likely to get another two.
Sweden and Finland are pressing ahead with their efforts to join the security alliance, despite Russian warnings of retaliation.
On Saturday, President Putin told Finnish counterpart Sauli Niinistö joining Nato would be a "mistake".
In a sign of what may come, Russia suspended electricity supplies to Finland, although a Finnish energy chief said it had not caused any problems.
On the ground, Ukrainian forces have been keeping up the pressure on Russia.
Its army has launched a counteroffensive in Izyum in Kharkiv region, military officials say.
Retaking the eastern city could complicate Russia's plans to capture the eastern Donbas region, the main focus of Russia since it withdrew from areas around the capital Kyiv.
Most significantly, the mayor of Kharkiv, Ukraine's second largest city, said Russian forces had withdrawn in the direction of the border.
One of our reporters in Ukraine has this assessment.
Kharkiv is a major victory for Ukraine
Joe Inwood, BBC News Lviv
On the outskirts of Kharkiv the retreating Russians left a parting gift.
Dergachi's Palace of Culture is now a smouldering ruin, thanks to a final barrage of rocket artillery.
But, it may be one of the last buildings in Ukraine's second city to suffer this fate.
Kharkiv is called a fortress, and with good reason. It has withstood more than two months of constant bombardment.
Its buildings and people have been battered, but never broken. Its defences never were breached
The city's mayor, Ihor Terekhov, told the BBC people are starting to return - and that the battle has been won.
"There were no Russian troops inside the city of Kharkiv. Russian tanks and armoured fighting vehicles were eliminated by Ukrainian fighters.
"And due to the efforts of the Kharkiv territorial defence and Ukrainian Armed Forces, the Russians have now withdrawn far from the city - towards the border," Terekhov said.
But, this was not a full-blown retreat as was seen around Kyiv. The Russian forces will hold lines further back, or re-join the fight elsewhere.
This is not a turning point in the war for Ukraine, but it is still a major victory.