It comes as the UK and US leaders meet in Washington to decide on whether to approve missiles for Ukraine to use against Russia. Six British diplomats have been expelled from Russia after being accused of "spying and sabotage". The country's FSB security service said they worked in the "political department" of the British embassy in Moscow. A Foreign Office spokesperson called the claims "completely baseless". Ukraine war latest: Putin threatens NATO with 'war' over long-range missiles They said the diplomats' had been expelled in August "following action taken by the UK government in response to Russian state-directed activity across Europe and in the UK". "We are unapologetic about protecting our national interests," the spokesperson added. The FSB claimed the Eastern Europe and Central Asia branch of the Foreign Office was now a "special service whose main task is to inflict a strategic defeat on our country". News of the expulsion comes as President Vladimir Putin warned against Ukraine getting approval to use Western-supplied long-range missiles against Russia. He said it would "significantly change the very essence, the very nature of the conflict" and "mean that NATO countries, US, European countries are at war with Russia".

British Prime Minister Sir Keir Starmer and US President Joe Biden will meet in Washington on Friday with a decision on approving the missiles believed to be imminent.

On the plane to the US, Sir Keir said Britain did not "seek any conflict with Russia".

"Russia started this conflict. Russia illegally invaded Ukraine. Russia could end this conflict straight away," he told reporters.

"Ukraine has the right to self-defence and we've obviously been absolutely fully supportive of Ukraine's right to self-defence - we're providing training capability, as you know," said the prime minister

"But we don't seek any conflict with Russia - that's not our intention in the slightest."

Ukraine's President Volodymyr Zelenskyy has for months been asking permission to fire long-range Storm Shadow missiles, as well as US-made ATACMS missiles, into Russia to limit its ability to launch attacks.

The dial may now have shifted after the US accused Russia of taking delivery of ballistic missiles from Iran, against the warnings of the West.

US secretary of state Antony Blinken called it a "dramatic escalation".President Biden has previously limited the distance US-provided missiles can be fired across the border amid concerns over an escalation.

Five weeks ago, Ukraine also launched an incursion into Russia's western Kursk region in a bid to gain an advantage in the war and divert Russian troops from Ukraine's Donetsk region.