"It could be a game changer. The longer Ukraine can strike, the shorter the war will be," Sybiga told reporters ahead of a UN Security Council meeting to mark 1,000 days since the Russian invasion of its Eastern European neighbor.

He argued that Kyiv has the "full right to strike military targets on the territory of Russia."

"It could have very positive impact on the situation on the battlefield," Sybiga added.

The use of long-range missiles, long sought by Ukraine, was approved two months before Biden leaves office to be replaced by US President-elect Donald Trump, who is seen as less inclined to help Kyiv.

Russia on Monday accused Biden of "fueling" tensions with the move.

UN Under-Secretary-General for Political Affairs Rosemary DiCarlo, referring to the green light, said that "all parties must ensure the safety and protection of civilians, regardless of their location."

DiCarlo, speaking on behalf of UN Secretary-General Antonio Guterres, went on to mark the "1,000 days of widespread death, destruction and despair that continue unabated for millions of Ukrainians."

She denounced the rise in civilian casualties and raised Russia's attack on Ukraine over the weekend, involving 120 missiles and 90 drones, which caused significant damage to Ukraine's power grid.

"The targeted devastation of Ukraine's energy infrastructure may make the coming winter the harshest since the start of the war," she warned.