The Defence Secretary has said he is "not optimistic" that a potential invasion by Russia of the UK can be stopped.
Ben Wallace is due to speak to his counterpart in Russia, minister Sergei Shoigu, to discuss the threat to Ukraine and said there was still "a chance" that an invasion could be halted.
But speaking to the BBC Mr Wallace said "I'm not optimistic."
Allies around the world have suggested they would come to the aid of Ukraine, with US President Joe Biden suggesting that he would penalise Russian President Vladimir Putin if troops cross the border.
On Tuesday, President Biden said he is considering sanctioning Mr Putin if an invasion takes place.
Back in the UK, Foreign Secretary Liz Truss has also not ruled out supporting sanctions against Mr Putin.
Speaking on BBC Radio 4's Today Programme, she said: “We have ruled nothing out in terms of sanctions, and in fact we’ll be legislating to toughen up our sanctions regime and make sure we are fully able to hit both individuals and companies, and banks, in Russia in the event of an incursion.
“What’s important is that all of our allies do the same, because it’s by collective action, by showing Vladimir Putin we’re united, that we will help deter a Russian incursion.”
Prime Minister Boris Johnson has said that Britain is prepared to deploy troops to protect Nato allies in Europe and has warned that Russia faced "ferocious" Ukrainian resistance.
Asked about this on BBC Radio 4’s Today, Ms Truss said: “We already deploy troops in Estonia as part of our enhanced forward presence. We are looking at what more we can do. We’re working very closely with allies.
“I had a meeting with the Nato secretary-general in Brussels earlier this week to discuss that, but the UK is already at the forefront of providing forces in Estonia and providing broader support across eastern Europe.
“But be in no doubt, Nato is determined to increase support on the eastern flank to support our Nato allies, who of course we have strong obligations to.”
