Citing two US officials familiar with the decision, CNN News reported on Sunday that US President Joe Biden authorized Ukraine to use powerful long-range American weapons to strike inside Russia.

The decision to allow the use of the Army Tactical Missile Systems, or ATACMS, inside Russia came after Moscow deployed nearly 50,000 troops to Kursk, the southern Russian region.

It is also worth mentioning that North Korea has deployed thousands of its troops to Kursk as part of Russia’s offensive, sparking concern from Biden and his advisers that their entry could lead to a dangerous new phase in the war, per CNN News.

“The change comes largely in response to Russia's deployment of North Korean ground troops to supplement its own forces, a development that has caused alarm in Washington and Kyiv,” Reuters reported, citing a US official and a source familiar with the decision.