General Motors ( GM) reported a surprise increase in U.S. sales for September, while its rival for the position as the world's largest automaker, Toyota ( TM), logged another decline.

GM said Tuesday it sold 334,974 light vehicles in September, up 4.3% on a same-day sales rate from the 334,025 it sold in September of 2006. There were 25 selling days last month, one less than a year ago.

The company said its retail deliveries totaled 255,274, up more than 7%. Detroit's automakers are cutting back on their lower-margin daily rental sales in favor of retail sales. Fleet sales fell more than 6% as part of a planned reduction by GM.

GM's car sales slipped 0.6%, to 131,371 vehicles on a same-day selling basis in September. Light-truck sales gained 7.7% to 203,603 units.

"Our retail share, which has been stable for two years, improved in the third quarter with all three months solid from a share standpoint," said GM in a press release. "Our market share performance of more than 25% over the last quarter demonstrates strong consumer acceptance of our new products and the continued progress we've made in our North America turnaround strategy."

Toyota, which has been feasting on the Big Three automakers' market share in North America, reported a 4.4% decline in U.S. sales for September, marking its third monthly sales drop in a row. It sold 213,043 vehicles in the U.S. during the month, compared with 222,950 a year earlier.

Expectations for auto sales in September were low across the board due to the weakening housing market in the U.S., which is viewed as a threat to consumer spending. Ford's ( F) results were in line with those tepid expectations. Its U.S. auto sales for September plummeted 21% to 189,863, compared with 238,848 in the same month last year.

Ford's sales to daily rental companies declined by 62%, while sales to individual retail customers fell 15%.

Ford's car sales slid 39% to 56,267 vehicles. Truck sales dropped 9% to 133,596 trucks. Despite the weakness, Ford pointed out strength in sales of its new crossover models, like the Ford Edge and Lincoln MKX, which spiked 96% in September.

"We continue to be encouraged by customers' strong response to our new products, which we're launching with high quality," said Ford in a press release. "Demand for our new crossovers continues to grow and contributes to our efforts to stabilize U.S. retail market share."

Elsewhere, Chrysler, which was recently taken over by Cerberus Capital Management, posted a 5% decline in sales to 159,799 units.

The U.S. auto industry has been focused lately on costs, with GM having reached a tentative agreement with the United Auto Workers on a historic new labor contract.

GM was rewarded by Wall Street last week when the agreement was announced, following a two-day strike by UAW workers. Expected to be ratified by a vote held by UAW members on Oct. 10, the agreement would create a union-controlled health care trust fund to free GM from its long-term obligations to retirees.

It also creates a two-tier wage structure, which will allow the company to pay new hires less money and reduce its labor costs over time.

The details of the agreement are still trickling out in the media. Meanwhile, Ford and Detroit's other big automaker, Chrysler, are waiting for the UAW to begin formal negotiations with them on a similar contract. It's unclear, though, whether executives and workers at those companies are willing to accept the same concessions that were made in the GM agreement.

The Wall Street Journal, citing unnamed sources, reported Tuesday that a majority of UAW officials on the Chrysler bargaining team raised objections to a two-tier structure allowing lower wages for new hires. It also said Ford and Chrysler may be unwilling to adopt GM's strategy of divulging significant details about new vehicle programs and timing.

For its part, Chrysler was not included when the UAW made previous concessions to GM and Ford on health care costs, so the company will be looking for a deal that accounts for that. Chrysler, recently taken private by Cerberus, is expected to report sales later.

Shares of GM recently were up 90 cents, or 2.5%, to $36.95. Ford shares were up 29 cents, or 3.5%, to $8.52. Shares of Toyota were down 85 cents, or 0.7%, to $117.90.