Live latest from Ukraine as United Nations holds emergency meeting

Boris Johnson has called Russia’s invasion of Ukraine a “disastrous misbegotten venture by President Putin” as the Kremlin’s forces continue to face fierce resistance on the ground.

Ahead of the United Nations holding a rare emergency meeting of its General Assembly over the crisis, the Prime Minister also told the Ukrainian President Volodymyr Zelensky that Britain would do all it could to get more arms to his military.

Mr Zelensky told Mr Johnson the next 24 hours would a “crucial period” for his country.

A Ukrainian delegation is due to meet the Russians “without precondition” on Monday on the border with Belarus, although Mr Zelensky has indicated he sees little prospect of any meaningful dialogue.

In the meantime, Russian and Ukrainian forces have again been engaged in heavy fighting ahead of the widely expected assault on the capital.

Ukrainian defenders have put up stiff resistance that appeared to slow the invasion, but a US official cautioned that far stronger Russian forces inevitably will learn and adapt their tactics as Russia’s assault goes on.

But the sanctions the UK, the US and other nations have imposed on Russia appear to be already having an impact.

By early Monday morning the ruble had already sunk by nearly 26% against the US dollar after Western nations moved to block Russian banks from the SWIFT global payment system.

President Putin sent shock waves through Western capitals with his instruction on Sunday to his top military leaders to put the strategic nuclear deterrent on a “special regime of combat duty”.

The US said it was “completely unacceptable” while a senior US defence official was quoted as warning the Russian leader had made any “miscalculation… much, much more dangerous”.

It came on a day in