The upset came as the US auto industry continues to rebound strongly, with the overall sales rate rising for the sixth consecutive quarter.

March sales increased 16.9 percent from a year earlier to 2.5 million vehicles, according to Autodata.

Meanwhile, rising oil prices in the wake of unrest in the Middle East has contributed to a strong shift towards smaller cars, automakers said.

Firm demand for Ford's updated truck line and its class-leading fuel efficiency helped boost sales 19.2 percent in March from a year ago, to 212,777 vehicles.

That was 6,156 more vehicles than GM sold after posting a 9.6 percent gain.

"Consumers are voting with their wallets," said Ken Czubay, who heads Ford's sales and marketing.

GM has been the top seller in the US market on an annual basis since 1931, according to Automotive News Data Center.

But its crown has been under a determined assault in recent years.

Toyota ended GM's 77-year reign as the world's largest automaker in 2008.

Ford last outsold GM in February 2010, but by a margin of just 471 vehicles.

GM also lost the top spot in July 1998 when it was hobbled by a strike at supplier Delphi Corporation and was outsold by Ford by 83,883 vehicles, the trade publication said.

"I don't think it shows a definitive turn, but how competitive the market is," Rebecca Lindland, an analyst with IHS Global Insight, told AFP.

GM remains the industry leader for the quarter, with sales up 24.1 percent to 592,545 vehicles as its share rose 0.7 points to 19.4 percent.

Ford's sales for the first three months of the year are up 15.9 percent at 496,720 vehicles but its share was down 0.6 points at 16.2 percent.

Both GM and Ford have undergone several rounds of intense restructuring after Asian makers wrested away market share and consumers shifted away from their former cash cows -- the gas-guzzling sport utility vehicles which fueled their profits in the 1990s.

Ford managed to get its books in order ahead of the 2008 financial crash and was able to survive the worst economic downturn in decades without resorting to government help.

GM emerged from a government-backed bankruptcy in July 2009 as a stronger but significantly smaller company.

"Our approach to the first quarter was to gain momentum and we did just that," GM's Johnson said in a conference call prior to the release of Ford's results.

"We'll continue to be very positive about our outlook, that we do have the right products at the right time and we continue to believe our company will continue to grow."

Chrysler, which also came out of taxpayer-funded bankruptcy reorganization in 2009, posted a 31 percent increase in March sales to 92,623 vehicles.

It was Chrysler's best month since May 2008 and the 12th consecutive month of year-over-year sales increases.

Toyota saw sales drop 5.7 percent from the heavily-incentivized March 2010 sales to 176,222 units.

While its quarterly sales were up 12.5 percent gain to 433,924 vehicles its share fell a full point to 14.2 percent in the first three months of the year.

"Our sales momentum continued in March and contributed to a strong first-quarter close," said Bob Carter, head of Toyota Motor Sales, USA.

"With improving purchase intentions and healthy inventory levels heading into April, we feel confident about our sales outlook."

Japanese rival Honda posted a 23.5 percent increase in sales to 133,650 vehicles in its sixth straight month of double-digit US sales growth. Its share for the quarter remained unchanged at 10.1 percent, according to Autodata.

Nissan's sales jumped 26.9 percent to 121,141 vehicles in March while its quarterly share rose 0.3 points to 9.3 percent.

Supply problems resulting from Japan's March 11 quake disaster did not appear to have made a significant impact on the US market even though Toyota, Honda, Nissan, Ford and GM have had to temporarily idle some US factories.

"Based on everything we see right now we don't see anything that's going to slow down the industry," GM's Johnson said.

"I don't see a big change in consumer demand unless something very dramatic comes out of Japan."