The UK foreign secretary, Liz Truss, has warned of a “dangerous moment for the world” as the "highly likely" prospect of a Russian invasion of Ukraine could embolden other countries such as Iran and China to expand their ambitions.
Speaking on Sky News, Truss said "we could be on the brink of a war in Europe, which would have severe consequences not just for the people of Russian and Ukraine but for the broader security in Europe", adding she was "very worried".
Her comments come as last-ditch efforts for a diplomatic situation to the crisis on the Russia-Ukraine border are sought by world leaders including Boris Johnson and Joe Biden.
A core pillar of the dispute is Russia's demand for the west to guarantee Ukraine will not join NATO, the defensive alliance of 30 countries.
But Truss has said it is not for Russia to determine Ukraine’s security arrangements.
She said: "The big risk is if there is an invasion into Ukraine, that would be hugely damaging for Russia and Ukraine, and it would further undermine the stability in Europe."
"President Putin has actively questioned why other countries in eastern Europe are members of NATO as well, so this I fear would not stop at Ukraine."
"This is an attack on the neighbouring states of Russia and other east European countries in trying to undermine the legitimacy of them being part of NATO."
Asked to expand on this point, the foreign secretary went on: "If we saw an invasion into Ukraine, there would be severe costs in terms of a long running conflict, we could see the undermining of security more broadly in Europe, we could also see other aggressors around the world see it as an opportunity to expand their ambitions too so this is a very dangerous moment for the world."
Asked to which other countries she was referring, Truss cited Iran and China as examples of potential aggressors.
Russia has amassed 100,000 troops on the Ukrainian border and Truss said an invasion of Ukraine "could be imminent and it is highly likely".
She said any conflict could be a "long, protracted war". When asked on Times Radio whether Russia has the military capacity to take and hold all of Ukraine, Truss said: "What we know is that the Ukrainians will fight. The UK has trained up 20,000 Ukrainian soldiers."
"We’ve supplied defensive weapons as have other allies. So, this will not be easy or simple for Vladimir Putin."
"This could be a long, protracted war, which would, of course, create huge damage for both the people of Ukraine and the people of Russia as well as threatening European security."
"However, Truss said Putin could still “change his mind".
She added: "We know or we believe that Vladimir Putin has not yet made a decision about whether to invade Ukraine. We think it’s highly likely."
"There are huge numbers of troops lined up on the border. We know that they’re in a position to attack imminently, but he can still change his mind and that is why diplomacy is so vital."