The SEC is in the early stages of developing rules that would require asset managers such as Fidelity Investments and BlackRock Inc to give regulators more information about their portfolios and conduct stress tests on their funds to determine how they would weather economic shocks, the WSJ said. (http://on.wsj.com/1q54tAx)

Among the SEC's concerns is some mutual funds' use of derivatives to boost returns, the Wall Street Journal said.

The SEC was not immediately available for comment outside regular U.S. business hours.

Reuters reported last week that the SEC, which 18 months ago began a review of fees paid among mutual fund advisers, fund companies and the brokerage firms that sell the funds, has uncovered a complex geometry of payments that may lead to sales of certain funds at the expense of others and is not clearly disclosed under regulators' current requirements.

(Reporting by Supriya Kurane in Bangalore; Editing by Kenneth Maxwell)