WASHINGTON—President Barack Obama this week will appoint Elizabeth Warren to a lead role setting up the new Bureau of Consumer Financial Protection, two Democratic officials said, a move that will allow the White House to avoid a messy Senate fight over her role.

Ms. Warren, currently a professor at Harvard Law School, will be named an assistant to the president and special advisor to Treasury Secretary Timothy Geithner in charge of launching the new agency and setting its mission. She was a candidate to be the agency's first...