President Barack Obama nominated Mary Jo White, a former United States attorney turned white-collar defense lawyer, on Thursday to chair the Securities and Exchange Commission, is accustomed to complex legal challenges. The SEC has a lead role in implementing changes on Wall Street.

White, 65, spent nearly a decade as United States attorney in New York, the first woman named to this post. Among her prominent cases, she oversaw the prosecution of the mafia boss John Gotti as well as Ramzi Yousef, the mastermind of the 1993 World Trade Center bombing.

She is now working the other side working as a white-collar defense lawyer, defending Wall Street firms and executives as a partner at Debevoise & Plimpton.

A White House official said the president would announce White's nomination during a ceremony in the State Dining Room Thursday afternoon.

Obama's decision to nominate White fuels expectations that the SEC will amp up its response to criticism that it hasn't been tough enough in overseeing the nation's securities laws and serving as Wall Street's sheriff.

If confirmed, White would be the first former prosecutor to head the SEC. Her prosecution background is expected to overcome any qualms about the brevity of her regulatory experience.

Bloomberg noted that White's nomination "is a departure for the agency, because it has tended to be run by lawyers steeped in financial policy making and the securities industry."