Moscow warns US missile authorization may mark new level of involvement in conflict for Washington

Russia would consider the White House's authorization for Ukraine to use U.S.-made longer-range weapons within Russia to be the beginning of a "qualitatively new round of tensions" between Moscow and Washington, a Kremlin spokesperson said on Monday.

"Allowing Kyiv to strike deep inside Russia with U.S. long-range missiles, if such permission has actually been given, will mark a qualitatively new round of tensions and level of Washington's involvement in the Ukraine conflict," Dmitry Peskov, a Kremlin spokesperson, said at his daily briefing.

President Joe Biden authorized the use of the weapons, ATACMS, or Army Tactical Missile System, within the Russian Kursk region, two U.S. officials told ABC News on Sunday. The missiles have a range of about 190 miles.

Ukraine had not as of Monday morning used the weapons against Russian forces within Russia, a senior defense official said.

Officials in Kyiv, including President Volodymyr Zelenskyy, had been calling for months for authorization to use such weapons within Russia. Kyiv has previously used the ATACMS to strike Russian bases within occupied Ukraine.

But the Biden administration had held back, even as Zelenskyy requested the authorization as he traveled to the White House for an official visit in September.

Peskov on Monday painted the apparent change in policy as an "obvious" signal that the Biden administration in its final months intends to "continue to add fuel to the fire."

He added that Moscow viewed the move as a way for the White House to "continue to provoke further escalation of tension around this conflict."

In a Monday morning briefing in Rio de Janeiro, U.S. Deputy National Security Adviser Jonathan Finer evaded questions from reporters about Biden's authorization.

"I'm not confirming any decisions that have or have not been made about U.S. assistance when it comes to these operational questions," Finer said. "I will say, with regard to the comments that came out of Russia, the fire was lit by Russia's invasion of Ukraine."

ABC News' Joe Simonetti, Lauren Minore, Patrick Reevell, Shannon K. Kingston, Luis Martinez and Alex Presha contributed to this report.