NEW YORK (CNNMoney.com) -- Ford said on Monday that its net loss widened to $5.8 billion in the third quarter - its worst quarterly performance in 14 years - as it took a hit from costs related to the restructuring of its key North American business.

The last time Ford posted a loss this big was in the first quarter of 1992, when it reported a net loss of $6.7 billion.

New Ford CEO Alan Mulally

Ford shares have slumped since hitting a 52-week high in September.

On a per-share basis, the company reported a net loss of $3.08 a share in the third quarter. In the year-ago period, it posted a net loss of $284 million, or 15 cents a share.

Ford also said it would restate its financial results from 2001 through the second quarter of 2006 due to a change in accounting of derivatives contracts.

New chief executive Alan Mulally called the results "unacceptable," but said Ford was committed to creating a viable business going forward.

"We know where we are with our business and we know why we are where we are," he said during a conference call with analysts.

Mulally, a former Boeing (Charts) executive, took over the CEO position from Bill Ford in September.

Excluding special items, Ford posted a loss of $1.2 billion, or 62 cents a share, versus consensus analysts' estimates of 61 cents a share on that basis.

Looking ahead, Ford executives said during the conference call that operating results are likely to worsen in the current quarter.

Ford (down $0.10 to $7.91, Charts) shares fell about 1.5 percent in midday trading.

Dearborn, Mich.-based Ford is in the process of restructuring its North America unit in an effort to stem market share losses in the U.S., and expectations were fairly low ahead of the earnings announcement.

"It's one of those things where you're used to being disappointed," Kevin Tynan, an auto analyst with Argus Research, said.

Ford, along with fellow automakers General Motors (Charts) and DaimlerChrysler's (Charts) Chrysler Group, have been struggling for U.S. market share against foreign competitors like Toyota Motor (Charts) and Honda (Charts).

The third quarter is traditionally a rough quarter for Ford, and company executives noted there were difficult comparisons due to incentives that were offered during the same period last year.

But they also acknowledged the company is losing market share not only in the U.S. but in other markets as well.

Ford's global auto unit posted a pre-tax loss of $1.8 billion, versus a loss of $1.3 billion in the year-ago period, as worldwide sales fell to $32.6 billion from $34.7 billion.

In its key North America auto unit, Ford's loss widened to $2 billion, versus $1.2 billion in the same period last year, due to falling sales and higher incentives. North American sales tumbled 15.4 percent to $15.4 billion.

Ford said it stands by the outlook it offered in mid-September, when it updated its turnaround plan and said it didn't expect its North America business to return to profitability before 2009.

At that time, Ford also announced moves to speed up and expand previously announced plant closings and staff cuts. Ford has a target of cutting 14,000 salaried jobs and reducing its hourly workers by 25,000 to 30,000 by 2008.

Analysts, however, have questioned whether the company's "Way Forward" plan is enough to curtail steady years of market share losses in the U.S.

Tynan expects the next two years to be challenging for Ford as it implements its turnaround plan. "Restructuring is going to get intense and expensive. Things could get worse before getting better for sure," he said.

In addition to weakness in North America, Ford's luxury unit has been struggling. Its Premier Automotive Group, which includes Jaguar and Land Rover, posted a loss of $593 million in the latest quarter, versus a $108 million loss in the same period last year.

But the company said its business in Europe and South America improved, helped by rising sales. Ford Europe sales rose 14 percent to $7.3 billion in the third quarter while South American sales surged 25 percent to $1.5 billion in the same period.

Ford's stock has tumbled about 17 percent since mid-September, when it touched a 52-week high of $9.48 a share.

Tynan does not own shares of Ford and his company doesn't do investment banking for the firm.

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