President Joe Biden has authorized Ukraine to use U.S.-supplied long range missiles to strike Russia, Reuters reported, citing sources.

This marks a U.S. policy shift coming at the tail-end of Biden’s time in office. President-elect Donald Trump has vowed to limit U.S. support for Ukraine and end its war with Russia.

The U.S. has provided $175 billion in aid to Ukraine — more than any other country — making American support crucial to Ukraine’s defense against Russia. A withdrawal of support could deal a major blow to Ukraine’s ability to resist Russia’s attacks.

On Sunday, Russia unleashed a barrage of missiles in Ukraine that killed at least seven people and caused severe damage to the power infrastructure.