Britain is planning to send tanks to Poland so more can be provided to Ukraine, Boris Johnson has announced as he warned Russia could still win the war.

The Prime Minister said that he wanted to “backfill” supplies of Soviet-era T-72 tanks being provided by Warsaw to help Ukraine fight off the Russian invasion.

“We are looking at sending tanks to Poland to help them as they send some of their T72s to Ukraine,” he said.

Speaking during a trip to India, the Prime Minister also revealed early plans for Western allies to provide “security guarantees” to Ukraine to avoid it ever being invaded again if the conflict came to an end.

The “quad” of Britain, the US, France and Germany are leading the discussions, with the idea being to promise Ukraine weaponry, training and intelligence in the long term.

Asked if Russia could eventually overcome Ukraine, Mr Johnson said: “The sad thing is that that is a realistic possibility.”

The US on Friday appeared to contradict the Prime Minister, with Daleep Singh, the deputy national security adviser, saying: “The assessment from where we stand is that … ultimately [Vladimir] Putin will see this is not the end game he bargained for.”