Vladimir Putin has warned that the West letting Kyiv use longer-range weapons to strike Russian targets would mean NATO would be "at war" with Russia.

Sir Keir Starmer is travelling to Washington to meet US President Joe Biden to discuss allowing Ukraine to use long-range Storm Shadow missiles following pleas from Kyiv.

The Russia’s President insisted his country would take “appropriate decisions” against any threats it faces.

Putin said: “If this decision is made, it will mean nothing other than the direct participation of NATO countries - the United States, European countries - in the war in Ukraine.

“This is their direct participation and this already, of course, significantly changes the very essence, the very nature of the conflict.

“This would mean that NATO countries - the United States and European countries - are at war with Russia.

“And if that is the case then, bearing in mind the change in the very essence of this conflict, we will take appropriate decisions based on the threats that will be posed to us.”

US Secretary of State Antony Blinken and Foreign Secretary David Lammy suggested in a visit to Kyiv on Wednesday that Putin had already escalated the war by seeking missiles from Iran.

Concern about escalation has been one of the reasons why permission has not been given to Kyiv to use Western long-range weapons to strike targets inside Russia.

But Mr Blinken said: “Just speaking for the United States, from day one …. we have adjusted and adapted As needs have changed as the battlefield has changed, and I have no doubt that we’ll continue to do that as this, as this evolves.”

Escalation was “one of the factors that we always consider but it’s certainly not the only factor and it’s not necessarily a dispositive factor”.

He added: “We’ve seen Russia now pursue and indeed escalate its attacks inside Ukraine, on civilians, on energy infrastructure, as well as on the Ukrainian military that’s defending its country.

“And we’ve now seen this action of Russia acquiring ballistic missiles from Iran, which will further empower their aggression in Ukraine. So if anyone is taking escalatory action, it would appear to be Mr Putin and Russia”

Mr Lammy said: “It is Putin who has escalated this week with the shipment of ballistic missiles from Iran and we’re seeing this new axis, Russia, Iran, North Korea. We urge China not to throw their lot in with this group of renegades.”