July 20 (Reuters) - The United States has imposed sanctions on Russian major copper producer Ural Mining And Metallurgical Company (UMMC) as a measure to "reduce Russia's revenue from the metals and mining sector," the Treasury and State departments said on Thursday.

Washington, along with Western allies, has imposed sanctions on hundreds of Russian companies and individuals since Moscow invaded Ukraine in 2022. On Thursday, it added nearly 120 individuals and entities to the list.

UMMC did not reply to a Reuters' request for comment. The deadline for ceasing transactions with UMMC is set by the United States for Oct. 18.

UMMC has not disclosed its copper output in recent years. As of 2020, it was producing around 40% of Russian copper, broadly in line with its peer Nornickel, which has not been targeted by the Western sanctions so far.

The London Metal Exchange (LME), the world's largest and oldest metals forum, restricted new copper deliveries from UMMC after Britain sanctioned its controlling shareholder in 2022.

Since October, copper produced by UMMC could only be delivered to LME-registered warehouses if the owner could prove to the exchange that it did not constitute a breach of sanctions.

As of June, when copper inventories in LME-registered warehouses saw large cancellations, the proportion of Russian-origin in the available stocks climbed to 66% from 33% in May.

However, the actual amount of Russia-made copper in the inventories fell to 22,750 metric tons last month from 29,600 in May, and the total available stocks have risen since then. (Reporting by Polina Devitt; Editing by Leslie Adler)