US STOCKS-S&P 500, Dow slip with investor focus on Middle East, but chipmakers climb

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* Micron gains on bullish brokerage update

* Energy shares slide as oil falls

* U.S. services sector activity better-than-expected in Dec

* Indexes: Dow off 0.3%, S&P down 0.1%, Nasdaq up 0.1% (Updates to late afternoon)

NEW YORK, Jan 7 (Reuters) - The S&P 500 and Dow declined on Tuesday as investor uncertainty persisted amid the U.S.-Iran standoff, while energy shares fell as oil prices gave up recent gains.

Exxon Mobil Corp and Chevron Corp declined, with U.S. oil prices falling after a recent rally on escalating tensions between Washington and Tehran. The United States killed a top Iranian military commander last week.

Chipmakers gained and helped to keep the Nasdaq in positive territory. The Philadelphia Semiconductor index rose, boosted by Micron Technology Inc, which jumped 7.5% after brokerage Cowen & Co upgraded the chipmaker to “outperform.”

Equity investors have been jittery since late last week, when a U.S. drone strike killed Iranian Major General Qassem Soleimani, taking major indexes off record highs.

“There are a number of headlines on the political front that the market is trying to get their arms around,” said Jack Janasiewicz, portfolio manager and strategist at Natixis Investment Managers’ Multi-Asset Portfolio Solutions group in Boston.

“The knee-jerk reaction is to have a little bit of volatility, a little of repricing some of the risks.”

The Dow Jones Industrial Average fell 76.09 points, or 0.27%, to 28,627.29, the S&P 500 lost 4.43 points, or 0.14%, to 3,241.85 and the Nasdaq Composite added 10.64 points, or 0.12%, to 9,082.11.

On the economic front, data showed new orders for U.S.-made goods fell in November, pulled down by steep declines in demand for machinery and transportation equipment, pointing to sustained weakness in manufacturing.

However, a reading on non-manufacturing sector activity for November came in better than expected.

Among gainers, Microchip Technology Inc rose 6.2% after raising the midpoint of its third-quarter sales forecast.

Apache Corp soared 25% after it made a major oil discovery, with France’s Total SA, off the coast of Suriname.

Declining issues outnumbered advancing ones on the NYSE by a 1.27-to-1 ratio; on Nasdaq, a 1.17-to-1 ratio favored decliners.

The S&P 500 posted 37 new 52-week highs and one new low; the Nasdaq Composite recorded 91 new highs and 15 new lows. (Additional reporting by Sruthi Shankar, Medha Singh and Susan Mathew in Bengaluru; Editing by Shounak Dasgupta and Jonathan Oatis)