Ukraine’s presence in Russia’s Kursk region has deteriorated sharply, with the Russian advance threatening Kyiv’s sole territorial bargaining counter at a crucial time in the war.

Military bloggers from both sides say Ukraine is on the back foot, while Ukraine’s army says Russian forces used a gas pipeline to launch a surprise raid in one area. Russia’s defense ministry on Sunday said its forces had captured four settlements in a couple of days.

Ukraine launched its shock incursion into Kursk in August, swiftly capturing territory in what was the first ground invasion of Russia by a foreign power since World War II.

As well as capturing land that could potentially be swapped for Russian-occupied territory, the campaign aimed to divert Moscow’s resources from the front lines in the east.

But since then, Ukraine has struggled to hold onto its territory in Kursk and faces a fundamentally transformed diplomatic picture, with United States President Donald Trump piling pressure on Kyiv to agree peace by halting US military aid and intelligence sharing.

Ukrainian and Russian military bloggers warn Kyiv’s hold on the region is more tenuous than ever, with Russian troops backed by North Korean forces launching incessant attacks.

CNN is unable to independently verify battlefield reports but such bloggers have previously provided an accurate account of the fighting.