Britain and its allies are "highly unlikely" to send troops to intervene if Russia invades Ukraine, Defense Secretary Ben Wallace told the Spectator magazine.

Britain and other G7 countries warned Moscow this week that invading the former Soviet state would have "huge implications", but Prime Minister Boris Johnson said Friday that his country will look into "diplomatic and economic" options to confront Russian "aggression".

"It is not a member of NATO so it is highly unlikely that anyone is going to send troops into Ukraine to challenge Russia," Wallace told the magazine in an interview this week.

"We shouldn't kid people we would. The Ukrainians are aware of that," he added.

Wallace suggested that Britain could assist Ukraine with "capacity building", but confirmed that concerns of "serious economic sanctions" were the most likely deterrent.

He suggested that Russia be cut off from the Swift international payment network.

The West claims that Moscow has deployed 100,000 troops near Ukraine. However, Ukraine and Russia both denied the claims. 

The Ukrainian statement came hours ahead of an announcement on the resignation of Defense Minister Andriy Taran, which reportedly came over his health situation.

"We aren't sure that he has made a decision but nevertheless his actions and his military preparations indicate that way... I think we should all be worried," said Wallace.