But as Ukraine prepares to meet with U.S. officials, Ukrainian soldiers say they are bracing for attacks to take advantage of a pause in U.S. intelligence.

Russia was storming the town of Sudzha on Sunday after special forces used a gas pipeline to surprise Ukrainian units as part of a major offensive to eject Ukrainian soldiers from the western Russian region of Kursk,

A Ukrainian-born, pro-Russian military blogger, said Russian special forces walked miles along the inside of a gas pipeline before surprising Ukrainian forces from the rear.

Russian forces on Sunday recaptured three more settlements in Russia's western Kursk region, the Defence Ministry said, part of an operation to evict Ukrainian troops holding chunks of territory seven months after a cross-border incursion.