The U.S. says there will be a "firm response" as Ukrainian forces holding ground in Russia's Kursk region now face North Korean troops "engaging in combat."

Russia has amassed a large force of tens of thousands — including recently arrived North Korean troops — to carry out an assault on the Ukrainian positions in Russia’s Kursk region expected in the coming days,

Russia attacked the Ukrainian capital Kyiv with a sophisticated combination of missiles and drones for the first time in 73 days on Wednesday, authorities reported, as the Pentagon said most of the North Korean troops sent to help Moscow’s war effort are fighting to drive Ukraine’s army off Russian soil in the Kursk border region.

A buildup of Russian troops in Ukraine’s southeast comes as uncertainty looms over how a Trump presidency will affect the war.

Ukrainian forces successfully repelled Russian attempts to break into the city of Kupiansk in Kharkiv Oblast, Ukrinfrom reported on Nov. 14, citing the General Staff of Ukraine's Armed Forces. Russian invaders failed to enter Kupiansk.

Meeting NATO Secretary General Mark Rutte in Brussels, Blinken also said the deployment of North Korean troops to help Russia in the Ukraine war "demands and will get a firm response". President-elect Trump,

U.S. Secretary of State Antony J. Blinken says the Biden administration is determined to help Ukraine keep fighting its war with Russia next year.