President Vladimir Putin has warned Russia would be “at war” with the United States and its allies if they lift restrictions on Ukraine’s use of long-range Western weapons.

Putin’s vow to follow such a move with “appropriate decisions” — his latest, perhaps most drastic attempt to draw red lines over NATO members’ backing for Kyiv — came on the eve of a meeting in Washington where the issue is expected to be high on the agenda.

British Prime Minister Sir Keir Starmer will hold talks with President Joe Biden later Friday, with the U.S. and its allies appearing open to letting Ukraine use long-range Western missiles to strike deep inside Russia — the culmination of a monthslong push by Kyiv.

“We are not talking about allowing or not allowing the Ukrainian regime to strike Russia with these weapons,” Putin said Thursday in comments to propagandist Pavel Zarubin. “We are talking about deciding whether NATO countries are directly involved in the military conflict or not.”

“This will mean that NATO countries, the U.S. and European countries are at war with Russia,” Putin said. “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.”

Putin’s comments were echoed by the speaker of Russia’s State Duma, Vyacheslav Volodin, in a Telegram post Friday. “NATO became a participant in military operations in Ukraine,” Volodin wrote. “They are waging war on our country.”

The Kremlin and Russian propaganda have been portraying the war in Ukraine as a clash with the West and NATO since the beginning of the full-scale invasion in Feb. 2022, and the latest threatening rhetoric from Putin appears to be an escalation of that strategy at a crucial moment.

Putin has repeatedly warned the West not to cross Moscow’s so-called red lines, which he warned could trigger nuclear conflict, but they have been repeatedly crossed without such a response from the Kremlin.

Ukrainian forces launched the first invasion of Russian territory since World War Two last month, only to be met with a relatively muted response. After more than a month, the Kremlin announced Thursday it had begun a major counteroffensive to retake some of the land seized in the Kursk border region.

As things stand, Kyiv only has permission to use Western-supplied long-range weapons such as American ATACMS and British Storm Shadows to strike Russian territory along its border, and only in response to attacks from these areas. It’s been pleading for that policy to change so it can strike military assets deeper inside Russia that are used to launch attacks on Ukrainian cities.

But Washington and its allies have been reluctant to allow that, fearing a major escalation.

That appears to have shifted in recent weeks.

Secretary of State Antony Blinken was in Kyiv on Wednesday with his British counterpart, and Biden indicated earlier this week that the U.S. was “working out” the issue.

Ahead of his meeting with Biden, the British leader’s office, told NBC News that Starmer told reporters the U.K. does not seek any conflict with Russia. But he noted: “Russia started this conflict. Russia illegally invaded Ukraine. Russia could end this conflict straight away.”

As he arrived in Washington, Russia’s FSB internal security service announced it had revoked the accreditation of six British diplomats in Moscow whose actions it said had signs of “reconnaissance and subversive work.”