Such an attack inside Russian territory "would represent the direct involvement of the United States and its satellites in hostilities against Russia", a foreign ministry statement said. President Joe Biden approved the use of the missiles on targets in Russia in a major change of US policy - two months before he is due to leave the White House.

France, which has provided long-range missiles to Ukraine, on Monday signalled allowing Kyiv to strike military targets inside Russia remained an option on the table. "We openly said this was an option that we would consider if it was to allow to strike a target from where Russia is currently aggressing Ukrainian territory.