As the fighting continued across the country the Foreign Secretary claimed Britain had to make “sacrifices now” to prevent further conflict.
Ms Truss told Sky News’s Trevor Phillips on Sunday programme that there will be an “economic cost” in Britain but that it was a price the country had to be prepared to pay.
She said: “This long-running conflict is about freedom and democracy in Europe.
“If we don’t stop Putin in Ukraine we are going to see others under threat – the Baltics, Poland, Moldova, and it could end up in a conflict with Nato.
“We do not want to go there. That is why it is so important we make the sacrifices now.
“Yes, there will be an economic cost here in Britain, there will be a cost in terms of access to oil and gas markets. I firmly believe that the British public understand the price we will pay if we don’t stand up to Putin now.”
Ms Truss also promised to support British nationals who wanted to go fight alongside the Ukrainian forces against the Russian invasion.
President Volodymyr Zelensky has promised to arm foreign volunteers to travel to his country to join the battle against Vladimir Putin’s forces.
Asked on the BBC’s Sunday Morning programme if she would support UK citizens who chose to answer the call, Ms Truss said: “That is something people can make their own decisions about.
“The people of Ukraine are fighting for freedom and democracy, not just for Ukraine but for the whole of Europe.
“Absolutely, if people want to support that struggle I would support them in doing that.”
The senior UK Government minister also warned that President Vladimir Putin could use “the most unsavoury means” in order to secure victory in Ukraine.
She said: “This could well be the beginning of the end for Putin. I fear that he is prepared to use the most unsavoury means in this war.
“He should be aware the International Criminal Court is already looking at what is happening in Ukraine. There will be serious consequences for him and for the Russian government.
“I fear this conflict could be very, very bloody.
“I urge the Russians not to escalate this conflict but we do need to be prepared for Russia to seek to use even worse weapons. I think it would be hugely devastating.
“We need to avoid this at all costs. This is why it is so important, the work we are doing to degrade the Russian military complex.”
It comes as Ukraine’s ambassador to the UK Vadym Prystaiko said he believes his country will hold out out for “as long as needed”.
He explained: “We’re holding. It’s been just four days. We have friends, we have support.
“They came with 150,000 troops. It’s totally not enough.
“People know how to create simple weapons.
“We’re not talking about complicated machinery, but simple weapons.”
He said 18,000 rifles that have been handed out have not yet been registered.
The ambassador said they have to fight “right now”, adding they can be registered later “when we win”.