RPT-US STOCKS-Futures lower on auto industry fate; Citi up

* Dimming prospects of US auto rescue unnerve markets

* Citigroup shares up on report of Saudi stake boost

* Jobless claims, Philly Fed survey on tap

* Wall St to open at lowest level in 5-1/2 years

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By Ellis Mnyandu

NEW YORK, Nov 20 (Reuters) - U.S. stock index futures signaled more losses for Wall Street on Thursday as investors worried that failure by U.S. automakers to get government aid would add to the economic woes and dim the profit outlook further.

Even so, investors took some comfort from news that Saudi Prince Alwaleed bin Talal would boost his stake in embattled Citigroup to 5 percent, a day after the bank's stock plummeted to a 13-year low. For details, see ID:nN20389289

But even after two days of pleas for aid by auto executives on Capitol Hill, the fate of General Motors , Ford and Chrysler hung on the balance.

With Congress winding down its session, the auto makers appeared to have made very little progress in convincing Washington to agree to a $25 billion rescue package that the automakers say is necessary to avert bankruptcy.

"One of the major problems here is what's going to be the effect on the economy if the automakers are not bailed out," said Peter Cardillo, chief market economist at Avalon Partners in New York. "Unfortunately, even some of the good news that's out there is not able to reverse negative market sentiment."

S&P 500 futures SPc1> slipped 6.50 points and were about even with fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures DJc1> dipped 39 points, and Nasdaq 100 NDc1> shed 6 points.

The automotive executives on Wednesday predicted a far-reaching calamity for the U.S. economy without a government lifeline. Before the bell shares of General Motors, a Dow component, slid more than 10 percent to $2.50.

Citigroup shares, however, rose more than 6 percent to $6.75 before the bell after Alwaleed bin Talal announced his plans for Citigroup, grappling with fallout from the mortgage crisis.

Worry about the fate of the U.S. auto industry, a major employer, was one of the catalysts for Wednesday's stock market plunge to a 5-1/2 year low, along with fears of more losses for the financial sector. Thursday's economic calendar includes reports on weekly jobless claims, due at 8:30 (1330 GMT), and a November survey of Mid-Atlantic factory activity is due out at 10 a.m. (1500 GMT), along with a report on leading indicators. (Reporting by Ellis Mnyandu; Editing by Kenneth Barry)