Russia's President Vladimir Putin has accused Nato of harbouring "imperial ambitions" after the western military alliance moved to admit Finland and Sweden as members.
Nato on Wednesday issued a formal membership invitation to the two Scandinavian countries during its summit in Madrid, where efforts to help Ukraine counter a Russian invasion dominated the agenda.
Nato leaders have channelled billions of dollars in military support to Kyiv since Mr Putin sent Russian troops into Ukraine in late February.
In the Turkmenistan capital of Ashgabat on Wednesday, Mr Putin said Ukraine and its people were a means for Nato to "defend their own interests".
"The Nato countries' leaders wish to ... assert their supremacy, their imperial ambitions," the Russian president said.
However, he said Nato membership for Finland and Sweden was not a problem for Russia.
"We don't have problems with Sweden and Finland like we do with Ukraine. We don't have territorial differences," Mr Putin said.
"There is nothing that could bother us about Sweden and Finland joining Nato. If Finland and Sweden wish to, they can join. That's up to them. They can join whatever they want."
But "if military contingents and military infrastructure were deployed there, we would be obliged to respond symmetrically and raise the same threats for those territories where threats have arisen for us", Mr Putin said.
The two countries abandoned a decades-long policy of neutrality after the invasion of Ukraine, which came after moves by Kyiv to join Nato.
Russia had always said Finland and Sweden joining the alliance would be destabilising for international security.
Russia's attack triggered economic sanctions against Moscow and a wave of support for Ukrainian President Volodymyr Zelenskyy's government, including deliveries of advanced weapons.
"Ukraine can count on us for as long as it takes," Nato chief Jens Stoltenberg said at the Madrid summit, which ends on Thursday.
The alliance announced a new strategic overview that focuses on the threat from Russia and says that Nato "cannot discount the possibility" of an attack on its members.
"Today in Madrid, Nato proved it can take difficult but essential decisions. We welcome a clear-eyed stance on Russia, as well as the accession for Finland and Sweden," Ukraine's Foreign Minister Dmytro Kuleba said.
Washington said it would shift the headquarters of its 5th Army Corps to Poland.
An army brigade will rotate in and out of Romania, two squadrons of F-35 fighters will be based in Britain, US air defence systems will be sent to Germany and Italy, and the fleet of US Navy destroyers in Spain will grow from four to six.
Britain also pledged another $1.2 billion in military aid for Ukraine on Wednesday, including air defence systems and drones.
Putin hits back at Johnson over 'toxic masculinity' comments
Mr Putin on Thursday rejected British Prime Minister Boris Johnson's claim that the Russian leader would not have invaded Ukraine if he were a woman. Mr Johnson called Mr Putin's war a "perfect example of toxic masculinity" and mocked his macho posturing.
At a news conference during a visit to Turkmenistan, Mr Putin pointed to former British leader Margaret Thatcher's decision to send troops into the Falklands as a rebuttal of Mr Johnson's theory.
"So, a woman took the decision to launch military action. Therefore it's not an entirely accurate reference from the British prime minister to what is happening today."
The Russian leader went on to criticise Britain's move, 40 years ago, to respond militarily to Argentina's attempt to seize the sparsely populated British-run islands in the South Atlantic.
"Where are the Falkland Islands and where is Britain?" Mr Putin said. "Thatcher's actions were dictated by nothing less than imperial ambitions and [a desire to] confirm their imperial status."
Moscow repeatedly rails against western military interventions in the likes of the former Yugoslavia, Afghanistan and Iraq as examples of western imperialism and hypocrisy.