A backlog of tankers is growing near Russia’s key oil port of Kozmino, the latest sign of disruption being wrought on the nation’s exports by sweeping U.S. sanctions.

On Jan. 10, the outgoing Biden administration designated 161 oil tankers along with vital traders and vessel insurers involved in the Russian export program. Oil futures surged as the market digested the supply implications of the move.

There are now nine oil tankers idling near the Russian Pacific port, the nation’s largest individual crude-export facility. While there are normally a few waiting at any one time, the number doing so now is bigger than normal, traders and shippers who monitor the exports said. A further 11 vessels are either approaching or have recently left.