LONDON (Reuters) - State-backed Royal Bank of Scotland (>> Royal Bank of Scotland Group plc) may need to pay $13 billion (8.33 billion pounds) to settle claims it misled investors in mortgage-backed securities, according to documents filed in a U.S. court.

The size of the potential settlement could make it more difficult for Britain's finance ministry to proceed with its plan to start selling the government's 78 percent stake in the bank in coming months, industry sources say.

The estimate was made in a filing by Philippe Selendy, a lawyer for Quinn Emanuel, which has brought the case for the U.S. Federal Housing Finance Agency and is based upon a previous judgement in a separate case involving RBS.

Nomura (>> Nomura Holdings, Inc.) and RBS were ordered last month to pay a collective $806 million for making false statements in selling mortgage-backed securities to Fannie Mae and Freddie Mac.

RBS has so far set aside 1.9 billion pounds ($3 billion) to deal with the claims, which relate to the sale of about $32 billion of mortgage-backed debt in the United States.

Analysts have told Reuters they expect RBS to have to pay anything between 3 billion and 9 billion pounds to settle the matter. RBS declined to comment.

(Reporting by Matt Scuffham; Editing by David Holmes)

Stocks treated in this article : Nomura Holdings, Inc., Royal Bank of Scotland Group plc