LONDON, May 20 (Reuters) - Russia's Arctic LNG 2 plant, which is subject to U.S. sanctions, has started production at its second train even after it has been unable to sell liquefied natural gas from a first train, a source familiar with the matter told Reuters.

Russian energy company Novatek NVTK.MM declined to comment.

It owns 60% in the plant located on the Gydan peninsula that juts into the Kara Sea and had been set to become one of Russia's largest LNG plants with an eventual output of 19.8 million metric tons per year at three trains.

Novatek began production at Arctic LNG in December 2023, but is behind schedule in supplying cargoes of the gas because of shortages of ice-class gas carriers and Western sanctions over Russia's war with Ukraine.

According to the source, Arctic LNG 2's first production train had been shut since October 11, as sanctions have prevented any sales.

Satellite images suggested that Arctic LNG 2 resumed some output at the end of March.

Russia's officials and businessmen have been cautiously optimistic about the prospects of sanctions easing after Donald Trump took office in the United States for the second term in January, ushering in the prospect of closer ties with Vladimir Putin.

Two separate sources said Novatek has been working with lobbyists to try to rebuild U.S. relations.

(Reporting by Marwa Rashad; writing by Vladimir Soldatkin; editing by Barbara Lewis)