When leaders of the North Atlantic Treaty Organisation (Nato) meet later this week near Cardiff, they will be faced with the lowest and chilliest ebb in East-West relations since the end of the Cold War a quarter of a century ago. How they choose to react to Russia’s continued interference in eastern Ukraine will shape the course of Nato for the next decade and will also redraw the map of Europe — just as the end of the Cold War and the collapse of the Soviet Union did in the East 25 years ago, and the implosion of the former Yugoslavia did in the South 20 years ago.

According to statements from Russian President Vladimir Putin on Moscow television on Sunday, he is endorsing a separatist breakaway independent republic in eastern Ukraine. In effect, he is endorsing the declaration of the republic of Don Bass made by separatists in Donetsk in April and endorsed by a poorly supported, illegitimate and unrecognised referendum hastily organised and rigged by those same baton-wielding pro-Russian sympathisers. Since then, the fighting has escalated, an estimated 2,000 have died, Malaysia Airlines MH-317 was downed and the West has increased its sanctions on Russia and pro-Kremlin apologists in Ukraine. But judging by Putin’s declaration of support for the independent state, the tragic events of the past four months have meant little. Perhaps the only difference now is that Russian military support for the separatists is more pronounced, with an estimated 1,000 Russian military personnel now operating on the ground of Don Bass.

When the Nato leadership meets, it will need to send a clear and unequivocal message to Putin that the West will not stand idly by while pro-Russian separatists carve up eastern Ukraine in a similar manner as to what had happened in Crimea. The European Union has given Russia a week to reconsider its involvement in Ukraine and has warned that tougher sanctions will follow. The US is continuing to provide arms to the government in Kiev. Until such a time as Putin purges this notion of a separate Ukraine, Nato, the European Union and the US need to keep the pressure on Moscow.