* Akerson accelerates exit after wife's cancer diagnosis
* CFO Ammann named president, ex-Cummins CEO named chairman
* Barra, 51, has 33 years' experience at GM
* U.S. Treasury exited its GM stake on Monday
DETROIT, Dec 10 (Reuters) - General Motors Co said on Tuesday Chief Executive Officer Dan Akerson will step down next month and be replaced by global product development chief Mary Barra, who will become the first woman to lead a global automaker.
The day after the U.S. Treasury announced it had sold the last of its GM shares, the company said in a statement that Akerson, who is also the chairman, will leave on Jan. 15, moving forward his planned departure by several months. His wife was recently diagnosed with an advanced stage of cancer.
Barra, 51, GM's executive vice president for global product development, purchasing and supply chain, was elected by the board as the next CEO and will become a director. Theodore Solso, 66, will succeed Akerson, 65, as chairman.
"I will leave with great satisfaction in what we have accomplished, great optimism over what is ahead and great pride that we are restoring General Motors as America's standard bearer in the global auto industry," Akerson said in a message to employees.
"My goals as CEO were to put the customer at the center of every decision we make, to position GM for long-term success and to make GM a company that America can be proud of again," he added. "We are well down that path, and I'm certain that our new team will keep us moving in that direction."
Under Akerson, GM had moved to eliminate some of its historic bureaucracy and inefficiencies, recovered its investment grade credit rating, and pared financial losses in its European business.
The U.S. Treasury's exit on Monday was another sign that could clear the way for GM to restore a common-stock dividend, a move investors have been hoping for.
Sources told Reuters last month that Akerson might step down in 2014. He was appointed CEO just before GM re-entered public markets on November 2010, following a $49.5 billion government bailout and bankruptcy reorganization.
Speculation on his exit gained steam in April, when GM disclosed in a securities filing that his compensation plan had changed. The CEO did not receive any restricted stock units last year "in acknowledgement of the possibility of his retirement before the completion of the three-year vesting period," which would be in 2015.
Some GM employees and analysts said Akerson gave Barra's candidacy a boost in September when he said it was "inevitable" that a woman would one day run one of the U.S. automakers. GM has several women executives in senior management as well as four women on its board.
With 33 years of experience at GM, Barra has risen through a series of manufacturing, engineering and senior staff positions, and is currently in charge of reducing the number of platforms on which GM builds its vehicles. A source close to Akerson's thinking who asked not to be identified said the CEO valued Barra highly for "bringing order to chaos" in the product development process.
"With an amazing portfolio of cars and trucks and the strongest financial performance in our recent history, this is an exciting time at today's GM," Barra said in the company statement. "I'm honored to lead the best team in the business and to keep our momentum at full speed."
Jared Rowe, president of industry research firm Kelley Blue Book, said it was great to see a woman named to lead GM.
"GM is in more than capable hands as we've seen some of the best products released under Mary Barra," he said. "Now that the company has also been freed from government ownership, Mary has the opportunity to see the company continue to develop vehicles that consumers want to drive while improving its continued profitability."
In other management changes, GM said Chief Financial Officer Dan Ammann, 41, would assume the title of president, while North American chief Mark Reuss, 50, would replace Barra as head of product development. Alan Batey, currently vice president of global Chevrolet, will replace Reuss as head of North America.
GM did not name a replacement for Ammann as CFO.
Vice Chairman Steve Girsky, 51, will move to a senior adviser role until leaving the company in April, GM said. He will remain on the board.
Solso is the former chairman and CEO of Cummins Inc and has been a member of the GM board since June 2012.
Shares of GM were up 5 cents at $40.95 on Tuesday morning on the New York Stock Exchange.