Restraint on all sides is necessary if the conflict in Ukraine is not to escalate

William Hague has an extremely challenging assignment in Kiev. As Russian troops fan out over the Crimean peninsula, it is only right that the Foreign Secretary should assure Ukrainians that they do not stand alone, and that the Western democracies support their right to determine their future, irrespective of Moscow’s bullying. Mr Hague should use his podium also to remind Vladimir Putin that Russia risks sinking into damaging diplomatic and economic isolation if it pursues a strategy of gobbling up bits of Ukraine on the basis of claims that ethnic Russians there feel endangered.

At the same time, the Foreign Secretary must avoid fighting talk. He will not be doing Ukraine’s new leaders any favours if he fails to inform them that Britain and the West can do little for them at this juncture except restate their principled support for the country’s territorial integrity.

This is not 1854, and Nato is not about to repeat the Anglo-French siege of Sevastopol. Militarily, the Russians hold Crimea in lockdown and no one can stop them from nudging a tame local assembly into declaring union – or reunion – with Russia; Crimea formed part of Russia until 1954. The fact that a referendum in Crimea on the region’s future has been called for 30 March suggests that this is the next card up the Kremlin’s sleeve. But, even if the Russians go further and encourage other areas in the west and south to break away, such as the Donetsk mining basin, there is not much that the outside world can do.

Mr Hague must tell the new leaders in Kiev to stop upping the ante with empty but inflammatory talk of “mobilising” against Russia. Ukraine is cash-strapped and in chaos, so how it could even contemplate launching a military operation against Russia is hard to imagine.

Nor do most people in the east or south necessarily want to be liberated. Many are Russian or Russian-speaking and look on the new leaders in Kiev as putschists, or even as banderas, the slang term for Ukrainian nationalists who backed Nazi Germany against the Soviet Union in the 1940s. That charge is unfair, but the Russian flag-wavers in Crimea and the Kremlin are on firmer ground when they point out that Viktor Yanukovych, however corrupt and awful, was a democratically elected leader – an uncomfortable fact that leaders in Western capitals appear to have forgotten.

If Western leaders seriously want to assist the people of this fractured country to recover a sense of unity, they would do well do ignore Crimea for now and concentrate on putting together a financial rescue package. With no investment, falling currency reserves and a danger that Russia will ratchet up the price of gas – or cut off the supply entirely – the country could go bankrupt, which would only bolster arguments that Ukraine is unviable

Ultimately, a three-way conversation on Ukraine’s internal organisation and external relationships, involving the West, Moscow and Kiev, is the only hope. Meanwhile, a century on from the outbreak of a war that began with a single shot fired in Bosnia, it is incumbent on all world leaders – European, American and Russian – to recognise that one false movement or even statement over Ukraine could have disastrous consequences.