Russia has amassed an estimated 130,000 trips near its border with Ukraine, which has sparked a desperate round of talks as Western leaders try to avoid a war.
Vladimir Putin has had his eyes on the country for almost a decade, while claiming the West is using NATO to undermine Russia.
The UK has already supplied 2,000 anti-tank missiles, body armour, helmets and combat boots to Ukraine and Prime Miknister Boris Johnson indicated he could go further.
Asked at the press conference in Brussels if he could authorise military support to an insurgency in Ukraine in the event of an invasion, he said: “We will consider what more we can conceivably offer.
“The Ukrainians are well prepared, there are things we’ve offered that they, in fact, don’t seem to need because they think they have them in enough numbers already."
He said the intelligence on the prospect of an invasion was “grim” but he did not believe Mr Putin had yet decided on whether to act.
“This is probably the most dangerous moment in the course of the next few days in what is the biggest security crisis Europe has faced for decades,” he said.
In a sign of the chilly atmosphere at the talks, Mr Lavrov said “ideological approaches, ultimatums and moralising is a road to nowhere” and accused Ms Truss of being ill-prepared for the negotiations.
Rejecting Ms Truss’s call for forces to pull back, Mr Lavrov said: “The demands to remove the Russian troops from the Russian territory cause regret. We don’t want to threaten anyone. It’s us who are facing threats.”
But he indicated force levels would fall once military exercises had been completed, at which point “the West will likely claim that it has forced Russia to de-escalate”.
Experts have warned the two country’s brinkmanship is an incredibly dangerous situation and one which may have lasting ramifications for the rest of the world, but how did it all begin?
Why are Russia and Ukraine in conflict?
Ukraine used to be run by Russia during the USSR’s reign, but when the Soviet bloc collapsed in 1991, it gained its independence.
Relations between the two countries have been on the boil since then and were even further heightened in 2014 when Russia annexed Ukraine’s Crimea territory.
Recently the hostilities have flared up again over a situation in Ukraine’s Donbass region coupled with Russian military escalation on the Ukraine-Russia border.
At the very heart of the conflict is Ukraine’s demographic makeup and geographical location.
As a former Soviet territory, Ukraine is divided into an eastern region, which has close historical and cultural ties to Russia, and the rest of the country which largely identifies as a sovereign Ukraine.
The east has been a hotbed for rebellion and pro-Russian sentiment, with rebels in the area allegedly receiving widespread support from Moscow – something which has played a key role in keeping the conflict thriving.
Since 2014 and the annexation of Crimea, about 13,000 people have lost their lives according to data from the United Nations, including ordinary civilians, Russian separatists and Ukrainian troops.
Why NATO is an issue
Mr Putin’s distrust of NATO is also a key driver, with one of the main aims of his presidency being to push back on its expansion to the east.
The Russian leader has said he wants international legal agreements to exclude any further NATO advances and the removal of backed weapons in Russia’s neighbouring countries.
He has said “Russia is seriously interested in obtaining reliable, legally fixed guarantees that rule out NATO expansion eastward and the deployment of offensive strike weapons systems in states adjacent to Russia.”
Why is Ukraine so important to Putin?
Mr Putin has wide ambitions for Ukraine and has openly threatened Ukraine’s statehood before.
He has previously said Russia and Ukraine are “one people” due to their former alliance in the Soviet Union.
Russia has long resisted Ukraine’s continuous moves toward Europe, including demanding it never becomes a part of NATO or the European Union - both of which are long-term ambitions of Ukraine.
Expert's view
Eastern Europe Analyst at The EIU, Matthew Sherwood, says the conflict has been “looking increasingly fragile” since 2021 began.
Mr Sherwood told the Express: “The conflict goes back to 2014 when Russia invaded and illegally annexed the Crimea peninsula.
“This was followed a few weeks later by fighting in the Donbas region of Ukraine between Ukrainian forces and separatists backed by Russia.
“Both events occurred after Ukraine’s Euromaidan Revolution (2013-14) that saw the ousting of the pro-Russia president, Viktor Yanukovich, who now lives in exile in Russia.
“After many years of conflict, the various parties agreed to a ceasefire in July 2020, which has been largely holding but looking increasingly fragile since the beginning of the 2021.”
East vs West
Mr Sherwood said: “The crisis is important globally because ultimately it pits Russia against the West, which does not recognise Russia’s annexation of the Crimea and also demands that Russia respects Ukraine’s sovereignty, as defined by the pre-2014 borders.
“While the conflict has been at a stalemate in recent years, relations between Russia and the West have been tested by the poisoning and killing of various anti-Kremlin figures.
“The attempted poisoning and now imprisonment of a Russian opposition leader, Alexei Navalny, has further soured relations and resulted in further tit-for-tat sanctions.
“It should be noted that since 2014, Russia has faced significant sanctions levied by the West, which have significantly curbed investment in its all-important hydrocarbons industry.”
