President Joe Biden, on his way out of the White House, has left President-elect Donald Trump a “parting gift” — an escalation of the war between Ukraine and Russia.

Late last week, Biden inexplicably ‘authorized’ Ukraine to utilize long-range U.S. weapons for strikes on Russian soil, which was meant by a reminder from President Vladimir Putin that any escalation could force Moscow to deploy nuclear weapons, even if on a limited basis.Biden’s authorization comes after reports earlier in the month said that North Korea had sent approximately 10,000 troops to Russia in preparation for introducing them into combat in Ukraine.

Administration officials hinted in May that the president could reverse course and authorize Ukrainian forces to use American-made and supplied weapons for strikes into Russia, but nothing developed over the course of the presidential election cycle. After Trump won, however, Biden changed his mind and gave the incoming administration a bigger problem.

The missiles, The Wall Street Journal reported, “could initially target positions in the Kursk region, where Russia has amassed more than 50,000 troops, including some 10,000 soldiers from North Korea, in an effort to recapture the territory.”The introduction of thousands of North Korean troops onto the battlefield and the expected Kursk operation led to a change in Biden’s calculus, U.S. officials and other people familiar with the deliberations said,” the report noted.

“Biden made the decision before he left Thursday for South America, one of his last foreign trips as president, said one of the people,” the report added.

It didn’t take long for Kyiv to take advantage of Biden’s authorization. CNN reported Tuesday that “Ukraine has fired US-made ATACMS missiles into Russia’s Bryansk region, Russia’s Defense Ministry said, in a major escalation on the 1,000th day of war.”

“The attack comes just two days after the Biden administration gave Kyiv the green light to use the longer-range American weapons against targets inside Russia,” CNN added.Kyiv did not immediately respond to the report. If confirmed, the attack would mark the first use of longer-range American weapons by Ukraine to strike deep into Russian territory, demonstrating Kyiv’s swift action in leveraging its newly-acquired capabilities.

At 3:25 a.m. local time (7:25 p.m. ET) on Tuesday, Ukraine launched six ballistic missiles at a facility in Bryansk, according to the Russian Defense Ministry. It claimed that American-made ATACMS missiles were used in the strike.

Russian air defenses reportedly intercepted five of the missiles, while a sixth was damaged. Debris from the damaged missile landed on the grounds of a military facility, sparking a fire that was later extinguished. No casualties or significant damage were reported, CNN said.

The decision to permit the use of Army Tactical Missile Systems (ATACMS) inside Russia had been debated for months among American officials. While some raised concerns about escalating the conflict, others worried about the depletion of U.S. stockpiles of the weapons.

Following the reported missile attack early Tuesday morning, President Vladimir Putin announced an update to Russia’s nuclear doctrine—just two days after President Biden approved the use of ATACMS.