KRASNOYARSK, Russia, April 1 (Reuters) – Russian aluminium giant Rusal has resumed supplies to the American market and aims to win back customers it lost due to U.S. sanctions by about September when the sector signs its supply contracts for 2020, its chief executive, Evgenii Nikitin said. Last autumn, Rusal, the world’s largest aluminium producer outside China, missed the traditional window for contracting sales for this year as it was still negotiating with the U.S. Treasury Department to be removed from a sanctions list.