Live updates: follow the latest news on Russia-Ukraine
Nato leaders including US President Joe Biden agreed new measures to defend the alliance and Ukraine against Russian aggression on Thursday with new troop deployments, additional aid and specialist equipment to deter a chemical, biological or nuclear attack.
It came on a day of three back-to-back summits of western leaders in Brussels in which the world's most powerful democracies sought to tackle the multi-tiered military, humanitarian and economic crisis unleashed by the war.
Allies heard a nine-minute plea from Ukraine's President Volodymyr Zelenskyy to end what he called a "month of the darkest suffering" as he raised the pressure on western leaders by demanding one per cent of Nato's tanks and planes as well as anti-ship weapons and multiple rocket launcher systems.
Mr Biden said the US would answer Mr Zelenskyy's call with "signficant, and increasing, amounts of security assistance", while Nato offered more military aid as well as medical supplies and decontamination training after Britain said the Russian leadership had "crossed the red line into barbarism".
It came as Ukrainian commanders reported progress in counter-attacks against the Russian offensive which entered its second month on Thursday.
Within their own bloc, Nato leaders approved the establishment of four new battalions in Hungary, Slovakia, Romania and Bulgaria to shore up the alliance's eastern flank in what Secretary General Jens Stoltenberg called a changed security environment.
The White House also unveiled a fresh round of sanctions on more than 400 Russian individuals and defence companies, while the G7 unveiled an initiative to blow the whistle on any attempts by Moscow to evade western embargoes.
The G7 also announced it would treat any gold transactions by Russia's central bank as coming under sanctions, after what a senior US official described as "market chatter" that Moscow was trying to sell gold reserves to prop up the rouble.
EU leaders meanwhile assembled at the European Council headquarters across town for a two-day meeting to discuss the bloc's response at which focus will shift to the economic and humanitarian fallout, amid disagreement over whether to sanction Russia's lucrative energy sector.
Other leaders talked about using sanctions to undermine Russia's war effort and persuade it to call off the attack on Ukraine.
"We must ensure that the decision to invade a sovereign independent country is understood to be a strategic failure that carries with it ruinous costs for Putin and Russia," Canadian Prime Minister Justin Trudeau said.
Mr Stoltenberg - who had his term in office extended by a year to September 2023 on Thursday - said Nato would not send planes into Ukraine because direct military engagement with Russia would only cause more death and destruction.
Telling allies that "security does not come for free", Mr Stoltenberg said Nato had agreed to submit plans before a Madrid summit in June on how they will reach the target of spending two per cent of GDP on defence.
The new battle groups and spending increases are part of what Mr Stoltenberg is calling a reset of Nato's defence posture to deal with a more hostile Russia.
Baltic leaders are especially concerned about the threat on their doorstep, particularly after the invasion exposed Belarus's close military ties to Russia, and want Nato's revised posture to ensure that they can defend themselves if they are attacked rather than waiting to be liberated by foreign troops.
"We don’t have any buffer any more," said Lithuanian President Gitanas Nauseda, whose country is sandwiched between Belarus and the Russian enclave of Kaliningrad. "We don’t have the time to react and this changes the military calculus of Nato entirely."
Nato help for Ukraine
Mr Biden landed in Belgium on Air Force One late on Wednesday, with a police cordon and barbed-wire fortifications providing the backdrop to his first visit to Europe since Russian President Vladimir Putin ordered the attack on Ukraine.
The talks were taking place in the shadow of what Mr Stoltenberg described as dangerous sabre-rattling by the Kremlin. He said any chemical attack would risk the spread of contamination into Nato territory but did not say whether this would be regarded as an attack sufficient to trigger the bloc’s Article 5 defence commitment.
Nato's offer of help on that front includes medical supplies, detection and protection equipment and training for decontamination and crisis management.
Western leaders were challenged to “keep the flame of freedom alive” by Britain’s Prime Minister Boris Johnson as he announced that the UK would send 6,000 defensive missiles and £25 million ($33m) in funding for the Ukrainian military.
Sweden said on the eve of the summit that it would double its military contribution with 5,000 additional anti-tank weapons and more de-mining equipment.
But there was no sign of Nato changing its mind on Mr Zelenskyy’s request for a no-fly zone in Ukraine’s skies, which western leaders say would escalate the conflict by bringing the alliance’s forces into direct combat with Russia.
“We will not send in Nato troops on the ground or Nato planes in the air,” Mr Stoltenberg said. “That will cause even more suffering, even more death, even more destruction.”
That position was set to disappoint Mr Zelenskyy as he tries to draw Nato out of its defensive posture by persuading it that Russia "does not intend to stop in Ukraine".
G7 and EU meet
The G7 meeting at Nato headquarters produced an agreement to work together on tougher sanctions enforcement after western powers imposed a wave of penalties on Russia’s economy.
The seven economies have agreed an initiative so that any Russian attempts to evade sanctions “can be dealt with effectively”, said US National Security Adviser Jake Sullivan.
The US also moved punish more individuals in the Kremlin’s inner circle by adding them to the sanctions list covering oligarchs and political figures.
Mr Sullivan said an “intense back-and-forth” between the US and its allies would culminate in an energy-related announcement on Friday as Europe tries to end its reliance on Russian oil and gas.
The G7 also discussed the effect on global food security of the war in Ukraine, one of the world’s top wheat producers.
On energy, Dutch Prime Minister Mark Rutte said he did not expect new sanctions to emerge from the meeting as leaders enter "more complex terrain" after consensus on the first four rounds of EU sanctions.
Irish leader Micheal Martin said he was open to further sanctions but that leaders had to ensure that any energy-related measures punish Russia rather than countries within the bloc.
German Chancellor Olaf Scholz, who chairs this year's G7 meetings and said another round of talks might take place before the main June summit, played down Russia's demand to receive energy payments in roubles by saying existing contracts already specified a currency.
As EU leaders discussed energy, Britain said it was listing another 65 Russian people and organisations including the mercenary Wagner group and a relative of Foreign Minister Sergey Lavrov.
European Council president Charles Michel said EU leaders would discuss support for Ukraine in the “dramatic circumstances” of the war as well as humanitarian assistance for the millions of refugees who have fled the country.
In a summit stretching into Friday, the EU’s 27 leaders are expected to endorse a new strategic blueprint that envisages a more security-conscious bloc armed with a 5,000-troop rapid response force.
But they are unlikely to find consensus on the question of Ukraine's application for EU membership, which is strongly supported by many countries in Eastern Europe but which western leaders have said will not be fast-tracked.
Mr Biden will head to Poland on Friday to visit US troops stationed on Nato’s eastern flank and speak to humanitarian experts in the country bearing the brunt of the refugee flow from Ukraine.