Speaking to reporters before chairing his final EU defence ministers' meeting -- 1,000 days after Russia's invasion -- Borrell called the US policy shift "very good news" for Ukraine.

"Today we will discuss about it, and I hope that all member states will follow the US decision," he said.

"I'm sure that they will follow the example of the US in order to allow the Ukrainians to use their arms to fight against the Russians inside Russian territory -- because it is from Russian territory where they are being attacked," Borrell added.

"It is fully in accordance with international law," he said.

While President Joe Biden has not spoken publicly on the matter, a US official has confirmed Washington would now allow Kyiv to use American-supplied long-range missiles for strikes inside Russian territory.

The shift puts the focus on other allies supplying Ukraine with long-range missiles -- notably the British and French Storm Shadow and SCALP missiles.

German Chancellor Olaf Scholz on Monday ruled out, once again, his country's sophisticated Taurus missiles being sent to Ukraine for use.

But French President Emmanuel Macron -- who previously voiced openness to letting Ukraine strike military targets inside Russia -- hailed the US decision as "a good one."

As he prepared to hand over the bloc's diplomatic helm to his designated successor Kaja Kallas next month, Borrell renewed his call for European unity and ramped-up defence spending.

He warned Russia's war -- which the West says is being militarily supported by Iran and North Korea, and "enabled" by China -- had changed the international security equation for good.

"No one can escape to the consequences of this war," Borrell said. "It has changed the world. It started the new era. So let's face the current circumstances and make all the member states united in support."