President Vladimir Putin has warned that if Western nations allow Ukraine to use long-range weapons to strike inside Russia then it will mean NATO would be “at war” with his country.

“This would in a significant way change the very nature of the conflict. It would mean that NATO countries, the US, European countries, are at war with Russia,” Putin told Russian state TV on Thursday.

“And if this is so, then, bearing in mind the change in the very essence of this conflict, we will make appropriate decisions based on the threats that will be created for us,” he said.

His comments come ahead of a meeting in Washington, DC, on Friday between British Prime Minister Keir Starmer and US President Joe Biden, who are expected to discuss giving Ukraine the go-ahead to strike targets inside Russia amid mounting concerns over its losses on the battlefield.

Ukrainian President Volodymyr Zelenskyy has repeatedly called for restrictions on Western-supplied, long-range weapons to be lifted so his forces can target airfields, ammunition depots and command centres deep inside Russia, also increasing the costs of the invasion for Moscow.

Speaking to reporters en route to the US, Starmer said, “Russia started this conflict. Russia illegally invaded Ukraine. Russia can end this conflict straight away. Ukraine has the right to self-defence”, according to British media reports.

It will likely be the last meeting between the US and British leaders before Biden leaves office and ahead of the US presidential election in November that will pit Democrat Kamala Harris against Republican Donald Trump.

Trump repeatedly refused to take sides on the war, which started with Russia’s full-scale invasion of Ukraine in 2022, during a debate with Harris this week, saying only: “I want the war to stop.”

Biden said he was “working” on Ukraine’s request as US Secretary of State Antony Blinken and British Foreign Secretary David Lammy made a rare joint visit to the Ukrainian capital, Kyiv, where they announced $1.5bn in additional aid.

Blinken wrapped up a three-nation, Ukraine-focused European tour in Poland on Thursday after hearing repeated appeals from Ukrainian officials to use Western-supplied weaponry for long-range strikes inside Russia.

“As what Russia’s doing has changed, as the battlefield has changed, we’ve adapted,” Blinken said at a news conference in Warsaw.

Biden has allowed Ukraine to fire US-provided missiles across the border into Russia in self-defence but has largely limited the distance they can be fired.

One of the key requests from Ukraine is to strike with US-produced Army Tactical Missile Systems (ATACMS).

But the Pentagon has said they wouldn’t be the answer to the main threat Ukraine faces from long-range Russian glide bombs, which are being fired from more than 300km (186 miles) away, beyond the ATACMS reach.

On Friday, Donald Tusk, the prime minister of NATO member Poland, which shares a border with Ukraine, said he was not worried by Putin’s comments.

“It is necessary to take all events in Ukraine and on the Ukrainian-Russian front very seriously, but I would not attach excessive importance to the latest statements from President Putin,” Tusk told a news conference.

“They rather show the difficult situation the Russians have on the front.”

Polish Foreign Minister Radowslaw Sikorski had previously said Kyiv should be allowed to use Western weapons in self-defence because “Russia is committing war crimes by attacking civilian targets”.

“Missiles that hit these civilian targets are fired from bomber aircraft from over the territory of Russia. These bombers take off from airfields on Russia’s territory,” Sikorski said.

Russian forces have ramped up pressure on the battlefield in eastern Ukraine’s Donetsk region and increased air attacks across the country.

Ukraine was pressing on with attacks in western Russia’s Kursk region following its surprise cross-border incursion on August 6, but Zelenskyy confirmed on Thursday that Moscow’s troops were mounting a counteroffensive.