US STOCKS-Wall St heads lower as trade deal optimism fades

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* Mnuchin sees extra tariffs in Dec if deal not signed

* China seeking more talks before signing deal - BBG

* Apple, chipmakers down slightly premarket

* Delta Air Lines falls 1% after Stephens cuts rating

* Futures down: Dow 0.29%, S&P 0.29%, Nasdaq 0.31% (Adds comments, details; updates prices)

By Sagarika Jaisinghani

Oct 14 (Reuters) - Wall Street was set to fall for the first time in four sessions on Monday on signs there was more hard work to be done before a partial trade deal with China announced by President Donald Trump on Friday could be sealed.

The S&P 500 and Dow Jones indexes ended Friday with their first weekly gain in a month after the U.S. President announced an accord he said would see both sides ease the tit-for-tat measures that have hammered global growth this year.

Trump, however, acknowledged the agreement could still collapse and a handful of media reports and comments from Treasury Secretary Steven Mnuchin left investors feeling less upbeat about what had really been achieved.

Shares of companies with a sizeable exposure to China, including Apple Inc, Nvidia Corp, Advanced Micro Devices Inc and Micron Technology Inc, slipped slightly in premarket trading after soaring on Friday. The iShares Phil Semiconductor ETF was set to open down about 0.5%.

Treasury Secretary Mnuchin said in a CNBC interview that he had "every expectation" that if a U.S.-China trade deal was not in place by Dec. 15, additional tariffs would be imposed, although he said he expected a deal to be agreed by then.

"If the Chinese want to keep talking, I think the Trump administration is willing to have them talk, but on Dec. 15 there will be new tariffs," said John Brady, senior vice president at R.J. O'Brien & Associates in Chicago.

At 8:54 a.m. ET, Dow e-minis were down 78 points, or 0.29%. S&P 500 e-minis were down 8.5 points, or 0.29% and Nasdaq 100 e-minis were down 24.25 points, or 0.31%.

Investors will now be looking at third-quarter earnings to gauge the impact of the trade conflict and a sluggish domestic economy on corporate America.

The reporting season kicks off on Tuesday, with the biggest U.S. banks expected to report a 1.2% decline in earnings due to falling interest rates, a raft of unsuccessful stock market flotations and macroeconomic tensions.

Bank of America Corp, Citigroup Inc, JPMorgan Chase & Co were down between 0.3% and 0.5% in premarket trading. The S&P 500 bank index had logged its best day in a month on Friday.

Overall, analysts are forecasting a 3.2% decline in profit for S&P 500 companies for the quarter from a year earlier, based on IBES data from Refinitiv.

Shares of oil majors Exxon Mobil Corp and Chevron Corp fell between 0.5% and 0.7%, tracking a 2% fall in oil prices.

Fastenal Co was down 2.5% after two brokerages downgraded the stock. The company had logged its best day in three decades on Friday after reporting strong results.

Delta Air Lines Inc fell 1.1% after Stephens cut its rating on the stock to "equal-weight" from "overweight", citing rising costs. It also cut its price target to $57 from $75.

Shares of U.S. construction and engineering company AECOM were an outperformer, rising 7.7% after it agreed to sell its management services unit to private equity firms Lindsay Goldberg and American Securities for about $2.4 billion. (Additional reporting by Arjun Panchadar and Medha Singh in Bengaluru; Editing by Sriraj Kalluvila)