NEW YORK (AFP) - US stocks managed small gains on Thursday despite a hit to major automakers from poor sales in May.

Shares of General Motors, Ford and Fiat Chrysler all took hits from the worse-than-expected slowdown across the US auto industry, with Fiat Chrysler the only one of the three to score a net gain for the month.

The Dow Jones Industrial Average finished the day a hair higher at 17,789.67 points.

The broad-based S&P 500 climbed 0.1 per cent to 2,099.33, and the tech-rich Nasdaq Composite Index added 0.1 per cent to 4,952.25.

General Motors shares lost 3.4 per cent after reporting an 18 per cent year-over-year fall in sales last month; Ford shares gave up 2.9 per cent on a 5.9 per cent fall in sales.

FCA US, the US unit of Italy's Fiat Chrysler Automobiles, turned in a 1 per cent sales gain but its shares tumbled 1.8 per cent.

US-traded shares of global brewing power AB InBev added to a two-week surge with a 2.2 per cent gain after Bloomberg reported that its merger with SABMiller would soon earn US Justice Department approval after an antitrust review.

That would likely come with divestment commitments and possibly protections for craft brewers threatened by the huge market power of AB InBev, Bloomberg reported.

Chinese online marketplace Alibaba tumbled 7 per cent after its largest shareholder, Japan's SoftBank, announced it would sell US$7.9 billion worth of Alibaba shares to pay down some of its own US$106 billion debt load.

Alibaba is buying back at least US$2 billion worth of the Softbank-owned shares, while US$500 million would be sold to an unnamed "major sovereign wealth fund", the Japanese company said.

The announcement weighed on shares of Yahoo, whose most valuable asset is its US$31 billion stake in Alibaba. Yahoo shares tumbled 3.4 per cent.