SEC Chair Mary Jo White will announce her position soon on whether to equalize duties for brokers and investment advisers in dealing with retail clients.
About a quarter of corporate debt is owned directly by retail investors, and 73 percent of the $3.2 trillion of outstanding municipal debt is owned by small investors.
Seeking to prevent graders from pandering to the bond issuers, who pay for the ratings, the rules include a strict prohibition on allowing sales motives to influence them.
The new requirements would apply to the $750 billion market for private mortgage-backed securities, which imploded in 2008 and financed just 1 percent of new mortgages in 2013.
The U.S. Securities and Exchange Commission should act immediately to eliminate two stock market pricing models that create conflicts of interest for brokers, Senator Carl Levin said in a letter to SEC Chair Mary Jo White.