U.K. Prime Minister Keir Starmer has announced that no final decision had been taken on the Storm Shadow missiles to let Ukraine fire missiles deeper into Russia, Politico has reported.

At a meeting in Washington the U.K. Prime Minister and U.S. President Joe Biden discussed, in particular, Ukraine's pleas to use British-supplied missiles against targets on Russian soil.

The two leaders met one-to-one for around 20 minutes in the Oval Office before a longer group meeting with aides, on strategic challenges including Ukraine and the Middle East.

Speaking to reporters after his dialogue with Biden Starmer hinted further developments may follow at the gathering of the UN General Assembly later this month.

"We'll obviously pick up again in UNGA in just a few days time with a wider group of individuals," he said.

The two leaders brushed off Russian President Vladimir Putin's recent threats saying such an act would put NATO countries "at war with Russia."

The U.S. President told reporters: "I don't think much about Vladimir Putin."

In response to a shouted question asking how soon he was prepared to let Ukraine fire missiles deeper into Russia, Biden added: "We're going to discuss that now."

Starmer insisted "this wasn’t a meeting about a particular capability," but added: "We've come to a strong position."