• Ukraine's President Volodymyr Zelenskyy warned any military confrontation with its neighbor Russia would amount to "a full-scale" war in Europe.
• Russia has amassed troops along its border with Ukraine and within its ally Belarus.
• Ukraine has both played down concerns of a confrontation, and warned of the possible consequences of a conflict on Europe's doorstep.

Ukraine's President Volodymyr Zelenskyy has warned that any military confrontation with its neighbor Russia would amount to "a full-scale" war.

Speaking after a meeting with U.K. Prime Minister Boris Johnson on Tuesday, Zelenskyy said that any conflict with Russia, which has massed more than 100,000 troops along its border with Ukraine, would affect the whole of Europe.

"There will be, unfortunately, a tragedy if the escalation against our state begins. That is why I openly say: this will not be a war between Ukraine and Russia — this will be a war in Europe, full-scale war, because no one will give up their territories and people anymore," the president said, speaking to reporters at a press conference with Johnson.

Earlier on Tuesday, Zelenskyy signed a decree to increase the size of Ukraine's armed forces by 100,000 troops over the next three years, and plans to raise soldiers' salaries. He insisted the move did not mean war with Russia was imminent, however.

"This decree [was prepared] not because we will soon have a war ... but so that soon and in the future there will be peace in Ukraine," Zelenskyy told lawmakers, according to Reuters, which noted that Ukraine's army is, as it stands, dwarfed by Russia's both in terms of manpower and military hardware.

'Nobody needs a war'

Ukraine's president, a newcomer to politics before his election in 2019, has had to tread a fine line between playing down widespread concerns about a possible confrontation with Russia in order to keep Ukrainian citizens and international investors calm, while also seeking military and financial aid from its Western allies.

Ukraine is not a member of the EU, or the military alliance NATO, but has a pro-Western government and the U.S., EU and NATO are keen to prevent it from being pulled into Russia's orbit by force.

Just how far NATO would go to defend Ukraine militarily is uncertain, however, and for now the West has threatened a raft of sanctions against Russia if it attacks Ukraine.

Western governments were widely criticized for failing to be tough on Russia after it annexed Crimea from Ukraine in 2014 and analysts share concerns that Russia is weighing up whether another invasion of Ukraine — perhaps of its eastern Donbas region where there are two pro-Russian, self-proclaimed republics — is worth the price of more potential sanctions that the West has threatened.

For its part, Russia has repeatedly said it does not plan to invade Ukraine but wants to defend its own security interests in the face of what it views as an expansion of Western military might on its doorstep, in Europe (and particularly, eastern Europe).

On Tuesday, Ukraine's Zelenskyy noted that "nobody needs a war, but we do not invite anyone with weapons to our land."

He added that "the state has changed, society and the army have changed and now there will be no occupation of any city or territory."

For his part, Johnson noted after his meeting with Zelenskyy in Kyiv that "it goes without saying that a further Russian invasion of Ukraine would be a political disaster, a humanitarian disaster, in my view, [and] would also be for Russia, for the world, a military disaster as well. The potential invasion completely flies in the face of President Putin's claims to be acting in the interests of the Ukrainian people."

Johnson reiterated that the U.K., U.S. and EU were ready to impose more sanctions on Russia, its key sectors and individuals, and that a package of sanctions and other measures would "be enacted the moment the first Russian toecap crosses further into Ukrainian territory."

This had been prepared "not as a show of hostility towards Russia, but as a demonstration that we will always stand up for freedom and democracy and Ukrainian sovereignty in the face of aggression."

Where does Russia stand?

Russia has repeatedly said it has no intention to invade Ukraine and Putin has defended the build-up of Russian troops along the border with Ukraine, saying Russia has a right to place military deployments wherever it likes on its own territory. It has also accused the West of whipping up "hysteria" over Ukraine.

Analysts say Russia's bigger aims are to stop Ukraine's gravitation toward the West, to maintain and bolster its own sphere of influence over former Soviet states and to stop any expansion of NATO into what it sees as its back yard.

To that that end, Russia made a series of security proposals to the U.S. in December with its principle demands being that NATO does not expand further to the east or admit Ukraine to the military alliance. It would also like to see NATO roll back its military deployments in eastern Europe.

The U.S. and NATO have refused these demands although both sides have said they will keep on talking in a bid to find compromises in other areas where both of their security interests could be met.

Commenting publicly on the geopolitical crisis for the first time in weeks on Tuesday, Putin accused Western nations of ignoring key Russian security concerns.

"It's already clear now ... that fundamental Russian concerns were ignored," Putin said at a press conference Tuesday, according to a Reuters translation.

Putin said that the U.S. wanted to "contain Russia" and that it was using Ukraine to do that, as he reiterated Russia's position that any possible membership of Ukraine in NATO would "undermine Russia's security."

"Let's imagine that Ukraine is a NATO member, it is fully packed of weapons, it gets advanced attack means like those in Poland and Romania and it starts an operation in Crimea," Putin said, describing Crimea, a part of Ukraine annexed by Russia in 2014, as a "sovereign Russian territory."

"Let's imagine that Ukraine is a NATO member state and it initiates a military operation. What should we do then, [should we] fight against the NATO bloc? Did anyone think at least something about that? Apparently not."