Ukrainian officials have not confirmed a retreat from the town in Russia’s Kursk region, parts of which were captured by Kyiv’s forces last summer.

Russian forces have driven the Ukrainian army out of the biggest town in Russia’s Kursk border region, officials claimed Thursday, as U.S. officials sought the Kremlin’s response to a proposed 30-day ceasefire in the three-year war that Ukraine has endorsed.

Russian forces have recaptured Sudzha, the largest town that Ukraine once occupied in the Kursk region, according to Moscow, threatening Kyiv’s sole territorial bargaining chip amid pressure to negotiate an end to the war.