U.S. Securities and Exchange Commission Chairman Christopher Cox said in an interview that his agency will propose new rules aimed at curtailing manipulative short sales of stocks in the next few weeks.

The proposals will be designed to ensure the smooth functioning of markets and to support equally the important role of bets on the upside and the downside, Cox said today.

A temporary measure, which expired Aug. 12, targeted so-called naked-short selling and included only the shares of Freddie Mac, Fannie Mae and 17 other brokerages.

Cox said the agency is looking at the consequences of the temporary measure and that the SEC is also considering rules that would curtail short selling in all companies, not just a select few.