GM CEO says economic outlook uncertain

"We are tied to the economy, so I am concerned about it," said Daniel Akerson, who has served as chief executive of the largest U.S. automaker since September 2010.

He also said the United States must address the issue of its rising federal deficit, and that it would shake global debt markets if the country were to default on its obligations.

(Reporting by Ben Klayman, additional reporting by Deepa Seetharaman; Writing by Scott Malone; Editing by Maureen Bavdek)