Speaking at a news conference in Prague after an informal meeting of NATO ministers on Friday, Blinken said: “And that went right to the president, and as you’ve heard, he’s approved use of our weapons for that purpose. Going forward, we’ll continue to do what we’ve been doing, which is as necessary adapt and adjust.”

The decision came as France and other European countries also indicated that Ukraine would be allowed to use their weapons on military targets inside Russia.

Russian President Vladimir Putin had warned on Tuesday of "serious consequences", stressing his country's nuclear strength, if Ukraine's Western allies loosened their policy.

Dmitry Medvedev, a former Russian president and current deputy chair of the country's security council, called the US move a "serious escalation" and warned that Russia would destroy any Western weapons used against it.

“Russia regards all long-range weapons used by Ukraine as already being directly controlled by servicemen from Nato countries. This is no military assistance, this is participation in a war against us,” he said, adding that Russia would destroy any western weaponry used to attack it “both in Ukraine and in the territory of other countries”.

The Nato secretary general, Jens Stoltenberg, dismissed warnings by Moscow that the decision to allow Ukraine to use western weapons to strike inside Russian territory might lead to an escalation.

“This is nothing new. It has been the case for a long time that every time Nato allies are providing support to Ukraine, President Putin is trying to threaten us to not do that,” Stoltenberg told reporters on Friday on the sidelines of a Nato foreign ministers’ meeting in Prague.