The West must be prepared for the "long haul" to ensure Russia's defeat in Ukraine, the Foreign Secretary has said.
In a major speech, Liz Truss made calls for allies to increase defence spending and supply tanks and warplanes to Kyiv.
Ms Truss argued that Vladimir Putin's invasion of Ukraine shows the need for a shake-up of the international structures which failed to prevent Russia's actions.
She said Western allies need to impose even tougher economic sanctions to increase Russia's isolation, including cutting off oil and gas imports "once and for all".
"There must be nowhere for Putin to go to fund this appalling war," she said in a speech at the Mansion House in the City of London on Wednesday night.
In a call to Western allies, she said: "We cannot be complacent – the fate of Ukraine remains in the balance.
"And let's be clear – if Putin succeeds there will be untold further misery across Europe and terrible consequences across the globe. We would never feel safe again.
"So 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."
She added: "We will keep going further and faster to push Russia out of the whole of Ukraine."
Defence Secretary Ben Wallace later reinforced the Foreign Secretary's view that Russian forces must be pushed out of "the whole of Ukraine", saying Britain would support Ukrainians in "both diplomatic efforts or military efforts".
Asked if the UK would help Ukraine win back its territory, the Defence Secretary told BBC Radio 4's Today programme: "We're prepared to help Ukraine stand by its sovereignty and defend itself however long that may take.
"There is no difference in the position of the United Kingdom since 2014, which is when Ukraine as a sovereign nation was invaded both in Crimea… and Donetsk.
"That needs to stop, that needs to be reversed."
In her speech, Ms Truss added that the UK will need to "learn the lessons of Ukraine".
"The UK sent weapons and trained Ukrainian troops long before the war started," she said.
"But the world should have done more to deter the invasion. We will never make that same mistake again.
"Some argue we shouldn't provide heavy weapons for fear of provoking something worse.
"But my view, is that inaction would be the greatest provocation. This is a time for courage not for caution."
Dominic Raab was non-committal on Wednesday when asked if the Foreign Secretary was right to say that the West should supply warplanes to Ukraine.
The Deputy Prime Minister also told BBC Radio 4's Today programme: "I certainly don't think we should be… avoiding providing support to Ukraine at this critical moment in the war. And the Foreign Secretary is right about that."
Pressed on whether she was right about providing the planes specifically, he said: "We need to listen very carefully to what the Ukrainians need and help with our allies to provide them with the military support, so that they win and so that [Vladimir] Putin loses, and that's part of it, so is the sanctions."
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