General Motors Co posted a weaker-than-expected fourth-quarter profit as disappointing performance overseas offset strong results in North America.

We obviously have work to do still and a long way to get to the objectives we ultimately want to get to, GM Chief Financial Officer Dan Ammann told reporters.

We clearly have work to do in Europe. We have work to do in the South America business. Frankly, we have work to do all around the company in terms of cost opportunity, he added.

Ammann said GM has not gone far enough in cutting costs in its European operations, but declined to provide a 2012 financial forecast for a unit that the No. 1 U.S. automaker has struggled to return to profitability. Overall, GM expects 2012 sales to top the $150.3 billion it saw in 2011 and its market share to remain flat.

Net income attributable to common shareholders was $500 million, or 28 cents a share, compared with $500 million, or 31 cents a share, in the year-ago quarter.

Excluding one-time items, GM earned 39 cents a share, two cents below analysts' average forecast in a poll by Thomson Reuters I/B/E/S.

Sales in the quarter rose 3 percent to $38 billion, compared with the $38.21 billion analysts had expected.

For 2012, GM expects to raise vehicle prices and contain cost inflation, but the sale of more cars than trucks will hurt profit margins.

GM said its U.S. defined pension plans earned asset returns of 11.1 percent last year, but they ended the year $13.3 billion pension shortfall in pension funding compared with $11.5 billion in 2010. GM expects returns of 6.2 percent in 2012 due to a greater shift to fixed income investments.

GM's shares fell to $24.44 in premarket trading from Wednesday's closing price of $24.93 on the New York Stock Exchange.

(Reporting By Ben Klayman and Deepa Seetharaman; Editing by John Wallace and Maureen Bavdek)