Ukraine's fate is hanging in the balance and its allies must brace for the long haul and "ramp up" military production including tanks and planes to help, Britain's foreign minister said on Wednesday.
Foreign Secretary Liz Truss also warned that China must play by international rules or be punished and that it was vital to send the right message to "aggressors" watching closely the response to Russia's invasion.
"We cannot be complacent -- the fate of Ukraine remains in the balance," she told diplomats and business leaders in London, deploring the "failure" of global security structures that should have prevented the war.
A victory for Russian President Vladimir Putin would have "terrible consequences across the globe", and more, heavier, weapons should be sent to Ukraine despite the risk of escalating the conflict.
"We must be prepared for the long haul and double down on our support for Ukraine.
"Heavy weapons, tanks, aeroplanes -- digging deep into our inventories, ramping up production. We need to do all of this.
"Inaction would be the greatest provocation."
Truss's comments at Mansion House in the City of London financial district echo those of Prime Minister Boris Johnson, who last week said the conflict could last until the end of next year.
On Monday, Defence Secretary Ben Wallace said Britain would provide Ukraine with armoured vehicles capable of firing missiles against invading Russian aircraft.
However, Johnson's press secretary clarified on Wednesday that the UK had no plans to send planes to the Ukraine given "specific challenges" of matching equipment and training.
But "we're not ruling anything out" including back-filling other countries that might donate their warplanes to Ukraine, the press secretary said.
US Defence Secretary Lloyd Austin said Ukraine can win the war against Russia if it has the right equipment.
Truss said economic sanctions against Russia must go further, including cutting off Europe's Russian energy imports "once and for all".
"There must be nowhere for Putin to go to fund this appalling war," she said, calling the Russian leader "a desperate rogue operator with no interest in international mores".
"The architecture that was designed to guarantee peace and prosperity has failed Ukraine," Truss said, adding the conflict "has to be a catalyst for wider change".
Heralding what she called "the return of geopolitics", Truss called for a world where "free nations are more assertive and self-confident".
"Aggressors are looking at what has happened in Ukraine and we need to make sure they get the right message," she warned.
Truss's wide-ranging speech also targeted Asia, where she deplored China's lack of criticism of Russia.
"China is not impervious," she said. "Their rise is not inevitable.
"They will not continue to rise if they do not play by the rules (and) we have shown with Russia the kind of choices that we're prepared to make when international rules are violated."
Truss called for "a global NATO" but insisted she did not want to extend membership to other regions.
"We need to pre-empt threats in the Indo-Pacific, working with allies like Japan and Australia to ensure that the Pacific is protected.
"We must ensure that democracies like Taiwan are able to defend themselves," she said, adding that the current NATO target of spending two percent of GDP on defence "must be a floor, not a ceiling".