The Defence Secretary has warned that Russia has a "a very significant force... that would overwhelm Ukraine should it be deployed".
Ben Wallace added that if Russia wants to "inflict violence and invade, they could do that".
Russia says some of its troops stationed near the Ukraine border are returning to their bases and has repeatedly denied it is planning to invade.
Speaking to Sky News, Mr Wallace continued: "The Ukrainians would put up a brave resistance.
"I made it very clear to the Russians the Ukrainians will fight, but those odds are overwhelming and no-one should delude themselves that they're not."
"We are in a position where we don't think President Putin has made a final decision.
"Judge with your own eyes at the scale of that Russian deployment on the borders of Ukraine… it's pretty clear that their intentions towards Ukraine are to change their behaviour, and indeed change NATO's relationship with Ukraine, and they're doing so at the threat of invasion, and I think that's something that we, as NATO, are here to challenge and also to deter."
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The Defence Secretary added: "I think what we haven't seen is evidence of withdrawal that has been claimed by the Kremlin, in fact we've seen continued build-up of things like field hospitals and strategic weapons systems.
"I think the reality is … that we'll take Russia at its word, but we'll judge them on their actions … and until we see a proper de-escalation, I think we should all be cautious about the direction of travel from the Kremlin."
Mr Wallace estimated that there are more than 100 Russian battalion tactical groups deployed on Ukraine's borders – "60% of the entire Russian land combat power".
"One hundred and thirty thousand-plus troops, both in Belarus and indeed Ukraine, but also out at sea there's effectively a significant flotilla of Russian and amphibious landing ships and, indeed, war ships and missile ships, and from a Ukrainian point of view they're fairly surrounded by a very large force of ready troops."