With two months left in office, the president for the first time authorized the Ukrainian military to use the system known as ATACMS to help defend its forces in the Kursk region of Russia.

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President Biden has authorized the first use of U.S.-supplied long-range missiles by Ukraine for strikes inside Russia, U.S. officials said.

The weapons are likely to be initially employed against Russian and North Korean troops in defense of Ukrainian forces in the Kursk region of western Russia, the officials said.

Mr. Biden’s decision is a major change in U.S. policy. The choice has divided his advisers, and his shift comes two months before President-elect Donald J. Trump takes office, having vowed to limit further support for Ukraine.

Allowing the Ukrainians to use the long-range missiles, known as the Army Tactical Missile Systems, or ATACMS, came in response to Russia’s surprise decision to bring North Korean troops into the fight, officials said.

Mr. Biden began to ease restrictions on the use of U.S.-supplied weapons on Russian soil after Russia launched a cross-border assault in May in the direction of Kharkiv, Ukraine’s second-largest city.

To help the Ukrainians defend Kharkiv, Mr. Biden allowed them to use the High Mobility Artillery Rocket System, or HIMARS, which have a range of about 50 miles, against Russian forces directly across the border. But Mr. Biden did not allow the Ukrainians to use longer-range ATACMS, which have a range of about 190 miles, in defense of Kharkiv.