US SEC probes dealings with sovereign funds -WSJ

* Probing banks, private-equity firms for bribery -WSJ

* Letters of inquiry sent to as many as 10 companies -WSJ

* Companies include Citi, Blackstone -WSJ

NEW YORK, Jan 13 (Reuters) - The U.S. Securities and Exchange Commission is investigating whether banks and private-equity firms violated bribery laws in their dealings with sovereign-wealth funds, The Wall Street Journal reported on Thursday.

The newspaper, citing people familiar with the matter, said the SEC has sent letters of inquiry to as many as 10 companies in the past week. Among the companies are Citigroup Inc (C.N) and private-equity firm Blackstone Group LP (BX.N), the report said.

One person familiar with a firm that received a letter said it was brief, indicating the investigation was at the early stages, the Journal reported.

Sovereign-wealth funds have in recent years invested in private-equity funds and the biggest Wall Street firms, taking stakes in Citigroup, Merrill Lynch & Co before its acquisition by Bank of America Corp (BAC.N), and Morgan Stanley (MS.N).

For example, in 2007, China Investment Corp, which manages more than $300 billion, invested in both Morgan Stanley and Blackstone.

An SEC spokesman declined to comment. (Reporting by Nadia Damouni; Editing by Gary Hill)