Budget shortfalls will restrict the U.S. Securities and Exchange Commission's work, its chairman said on Tuesday, limiting the SEC's ability to police credit rating agencies, ferret out fraud and write rules to supervise derivatives markets. Cutbacks from Congress could delay rules to right the financial system after the 2007-09 economic crisis and put on hold reforms aimed at bolstering the integrity of stock markets after the May 6 "flash crash," Mary Schapiro said in an interview. "We will have to take some more steps to cut back," Schapiro said. "At this stage it will impact our work."