GM's board and CEO Fritz Henderson parted ways Tuesday, the board upset that the automaker's turnaround wasn't moving more swiftly and Henderson frustrated with second-guessing, two people close to the former CEO said.

Board Chairman Ed Whitacre Jr, the former head of AT&T Inc, will take over as CEO while a global search is conducted.

It was unclear whether Henderson or the board moved first in the surprise resignation, which came just hours before Henderson was to be the high-profile keynote speaker at the Los Angeles Auto Show.

Agreed to step down

At a hastily called news conference at General Motors Company's downtown Detroit headquarters, Whitacre would not answer questions, but said the board and Henderson agreed that he should step down.

Whitacre thanked Henderson, 51, a lifelong GM employee, for his leadership and said the company is on the right path toward offering high-quality cars and trucks worldwide.

"We now need to accelerate our progress toward that goal," the 68-year-old Whitacre said in a brief appearance.

Both men were chosen for their jobs by the US government, which owns more than 60 per cent of the Detroit automaker in exchange for giving it billions in loans. But Henderson is a GM insider, while Whitacre had no car experience before taking the GM chairmanship.

"I don't think this has much to do with Fritz Henderson's performance, I think it's just the wrong time to be a GM lifer," said Logan Robinson, a former Chrysler attorney and professor of corporate governance at University of Detroit Mercy.

Henderson, who rose through GM's ranks over a 25-year career, took over in March after the government forced out former CEO Rick Wagoner.

- AP