TOKYO, March 29 (Reuters) - Nomura Holdings Inc said on Monday it discovered a case that could subject one of its U.S. units to “a significant loss” arising from transactions with a U.S. client. The estimated amount of the claim against the client is approximately $2 billion based on market prices as of March 26, the Japanese brokerage and investment bank said in a statement. Nomura said it is still assessing the impact of the loss on its consolidated earnings. (Reporting by Makiko Yamazaki; Editing by Christian Schmollinger)