KYIV, Ukraine (AP) — Ukraine’s military claimed it struck a major oil terminal Monday in Crimea that provides fuel for Russia’s war effort as Ukrainian President Volodymyr Zelenskyy said the war has entered a key phase.

Both sides are facing the issue of how to sustain their costly war of attrition — a conflict that started with Russia's full-scale invasion of Ukraine in February 2022 and that shows no signs of a resolution.

Ukraine’s General Staff said on social media that the oil terminal in Feodosia, on the south coast of the Russia-occupied Crimea Peninsula, has been supplying the Russian army with fuel and that the strike was part of an ongoing effort to “undermine the military and economic potential of the Russian Federation.”

Russian-installed authorities in the city of Feodosia on the coast of the Black Sea reported a fire at the terminal on Monday morning but did not say what might have caused it.

Ukraine has increasingly targeted rear areas that are essential for Russia’s onslaught, now deep into its third year. It has developed long-range drones that have hit oil depots and refineries as well as armories.

Ukraine's aim is to impair Russia’s ability to support its front-line units, especially in the eastern Donetsk region where the main Russian battlefield effort is stretching weary Ukrainian forces.

Kyiv is still awaiting word from its Western partners on its repeated requests to use the long-range weapons they provide to hit targets on Russian soil.

Developments on that question could come next weekend at Ramstein Air Base in Germany, when defense leaders from the 50-plus partner nations that coordinate military aid to Ukraine are due to meet.

The conflict has largely been a war of attrition, which requires large amounts of ammunition. Late on Sunday, Zelenskyy said the war is in “a very important phase” as the Ukrainian army works hard to hold the bigger Russian forces at bay in the east while also holding ground in Russia’s Kursk border region, which it captured two months ago.

Ukraine needs to “put pressure on Russia in the way that’s necessary for Russia to realize that the war will gain them nothing," Zelenskyy said in a video statement.

“We will continue to apply even greater pressure on Russia — because only through strength can we bring peace closer,” he added.

Meanwhile, Russia fired six missiles of various types and 74 Shahed drones at Ukraine overnight, Ukraine’s air force said.

Missile debris fell in three districts of Kyiv, causing minor damage to civilian infrastructure and starting a fire, Mayor Vitalii Klitschko said. He said nobody was hurt. Three missile fragments fell on a kindergarten, he said without elaborating.

Russia’s Defense Ministry said it shot down almost two dozen Ukrainian drones overnight.

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Follow AP’s coverage of the war in Ukraine at https://apnews.com/hub/russia-ukraine