• The U.S. decision, reported by NBC News, marks a major reversal in Washington policy a mere two months before the mandate expiry of President Joe Biden, who has steered U.S. engagement in the Ukraine conflict since Russia's wholescale invasion in February 2022.
• "It is obvious that the outgoing administration in Washington intends to take steps to continue adding fuel to the fire and continue to provoke tension around this conflict," Kremlin Spokesperson Dmitry Peskov said earlier on Monday, according to Reuters.
• Analysts at the Institute for the Study of War warn that Washington's limited authorization could prove insufficient to materially alter the course on the battlefield.

The Kremlin has lashed back against a White House decision to now allow Ukraine to use U.S.-made long-range weapons for limited strikes inside Russian territory.

The decision, reported by NBC News, marks a major reversal in Washington policy a mere two months before the mandate expiry of President Joe Biden, who has steered U.S. engagement in the Ukraine conflict since Russia's wholescale invasion in February 2022.

Previously, the Biden administration had limited the deployment of American-made long-range arsenal to the Ukrainian battlefield, but had green lit Kyiv's use of U.S.-made High Mobility Artillery Rocket Systems (HIMAR) in cross-border attacks to defend Ukraine.

The latest authorization follows the deployment of North Korean troops to support Moscow in the stagnating conflict, along with what Ukrainian President Volodymyr Zelenskyy qualified as "one of the largest Russian strikes" against his country over the weekend.

"It is obvious that the outgoing administration in Washington intends to take steps to continue adding fuel to the fire and continue to provoke tension around this conflict," Kremlin Spokesperson Dmitry Peskov said earlier on Monday, according to Reuters.

"If such a decision was really formulated and communicated to the Kyiv regime, then, of course, this is a qualitatively new round of tension and a qualitatively new situation from the point of view of the US involvement in this conflict," he added, in Google-translated comments reported by Russian state news agency Ria Novosti.

Ukraine depends on Western allies for military and humanitarian aid, including the provision of weapons — which NATO members have largely supplied for defensive purposes on Ukrainian grounds, amid fears of further war escalations and Russian retaliation. Speaking to journalists on Sept. 12, Kremlin leader Vladimir Putin had warned that a then-potential decision on behalf of any NATO country to allow Ukraine the use of long-range weapons against targets on Russian soil would amount to direct participation in the war.

"The issue is not about allowing the Ukrainian regime to strike Russia with these weapons or not. The issue is about making a decision: NATO countries directly participate in the military conflict or not. If this decision is made, it will mean nothing other than the direct participation of NATO countries — the United States, European countries — in the war in Ukraine," Putin said at the time, according to Russian state news agency Tass.

Yet analysts at the Institute for the Study of War warn that Washington's limited authorization could prove insufficient to materially alter the course on the battlefield.

"The partial lifting of restrictions on Ukraine's use of Western-provided long-range weapons against military objects within Kursk Oblast will not completely deprive Russian forces of their sanctuary in Russian territory, as hundreds of military objects remain within ATACMS range in other Russian border regions," they said in a note, with reference to the U.S. long-range Army Tactical Missile System.

They added that "Russian forces will benefit from any partial sanctuary if Western states continue to impose restrictions on Ukraine's ability to defend itself and that the US should allow Ukraine to strike all legitimate military targets within Russia's operational and deep-rear within range of US-provided weapons – not just those in Kursk Oblast."

"The only way to truly stop this terror is to eliminate Russia's ability to launch attacks. And this is absolutely realistic," Zelenskyy said on social media on Monday, without directly referencing the reports of the U.S. permission. "It is not just defense; it is justice— the right way to protect our people. Any nation under the attack would act this way to defend its citizens. We must do the same, together with our partners. Russia must be left with no capacity for terror."

It remains to be seen whether European countries will follow Washington's suit over Kyiv's use of their weapons. CNBC has reached out to the foreign ministries of major Western NATO allies Germany, France and the U.K. for comment.

EU foreign affairs ministers are meanwhile gathering in Brussels on Monday to hold talks that will also touch on the Ukraine conflict.

"I've been saying once and again that Ukraine should be able to use the arms we provided to them, in order to not only to stop the arrow, but also to be able to hit the archers. I continue to believe this is what has to be done. And I'm sure will be discussed once again. I hope members will agree on that," EU foreign policy chief Josep Borrell said prior to the meeting.

Such a decision raises questions over the extent of Ukraine's current long-range missile arsenal to support direct attacks, at a time when NATO braces for the White House return of U.S. President-elect Donald Trump – who has previously pledged to end the war in Ukraine within a day of assuming power, without supplying details.

Nevertheless, the U.S. authorization "could mark a paradigm shift in the war," Tytti Tuppurainen, member of the Finnish parliament, told CNBC's Silvia Amaro on Monday.

"If it is true … I think we welcome that, we welcome that full-heartedly. If it is one thing we regret, it is that it comes so late," she added. "Europe has to stand up now. This is a critical moment. This is certainly a wake-up call for Europe. From the U.S. side, the election of Donald Trump tells us that we have to take the responsibility of our own destiny, and if Russia wins in Ukraine, it means that Russia will only continue."