* Apple weighs on U.S. stocks in holiday-shortened week
* Oil spikes to highest since 2015; gold also rises
* U.S. 2-year yield at 9 year highs; yield curve flattens
* Bitcoin rebounds after losing a quarter of its value (Updates to U.S. market close)
By Trevor Hunnicutt
Dec 26 (Reuters) - Investors scooped up commodities on Tuesday during a holiday-shortened week, but took a far more mixed view of equities as shares of Apple Inc sagged.
The main equity gauges on Wall Street closed down following a 2.54 percent drop in Apple's shares on reports of weak iPhone X demand.
Many markets around the world, including in parts of Europe and Asia, were shut on Tuesday after the Christmas Day holiday, and trading volumes were light. U.S. stock exchange share volumes for the day were their lowest since Nov. 24, another post-holiday trading session, according to Thomson Reuters data.
Commodities firmed, with oil moving to its highest since 2015, supported by an explosion on a crude pipeline in Libya and voluntary supply cuts led by the Organization of the Petroleum Exporting Countries.
U.S. crude rose 2.21 percent to $59.76 per barrel and Brent was last at $66.19, up 2.26 percent on the day.
Gold prices hit more-than-three-week highs, and palladium hit its highest since February 2001 on supply worries. Spot gold added 0.7 percent to $1,283.15 an ounce.
Bitcoin rebounded from a brutal selloff last week. The wild-trading digital asset gained 13.79 percent as of Tuesday afternoon, after sinking by more than a quarter from Dec 16 to 25.
Apple put a damper on an equity market that has posted double-digit percentage gains in 2017 on the back of a U.S. tax bill signed into law last week and stronger sales that were expected to extend into the holiday season.
Yet, bearish brokerage calls on iPhone X demand pushed the company's shares to their worst single-day percentage fall since Aug. 10. The company will slash its sales forecast for its flagship phone in the current quarter to 30 million units, down from what it said was an initial plan of 50 million units, Taiwan's Economic Daily reported, citing unidentified sources.
The news hit shares of Apple suppliers, too, including Broadcom Ltd, Skyworks Solutions Inc, Finisar Corp and Lumentum Holdings Inc.
"There probably are a good number of U.S. investors that have slight to moderate overexposure to domestic stocks - we've had a great performance year," said Invesco Ltd Chief Global Market Strategist Kristina Hooper.
"It could be an opportunity to do some profit-taking, a little bit of trimming, and moving to areas that have lower valuations."
The Dow Jones Industrial Average fell 7.85 points, or 0.03 percent, to 24,746.21, the S&P 500 lost 2.84 points, or 0.11 percent, to 2,680.5 and the Nasdaq Composite dropped 23.71 points, or 0.34 percent, to 6,936.25.
MSCI's measure of stocks across the globe shed 0.05 percent.
Volatility, notably lacking in U.S. markets in 2017, gained during the light trading day. The CBOE Volatility Index, an options-based gauge, rose 0.35 points, to 10.25.
TWO-YEAR YIELDS RISE
Two-year U.S. Treasury yields rose to nine-year highs, exacerbating a collapse of the gap in yields between short and long-term bonds. The gap between 2-year and 10-year yields shrank to 56.7 basis points as the United States sold $26 billion in the shorter-duration notes.
Benchmark 10-year notes last rose 5/32 in price to yield 2.472 percent, from 2.488 percent late on Friday. The 2-year note last fell 1/32 in price to yield 1.9033 percent, from 1.895 percent the previous trading day.
Currencies changed little during the day. The dollar index , tracking the U.S. unit against a basket of major currencies, fell 0.09 percent, with the euro also down 0.05 percent to $1.1862.
Sterling was last trading at $1.3375, up 0.05 percent versus the greenback, while the Japanese yen strengthened 0.07 percent on the day.
Japan's households spent more than expected in November while consumer inflation ticked up and the jobless rate hit a fresh 24-year low, according to data earlier on Tuesday, offering the nation's central bank some hope an economic recovery will drive up inflation to its 2 percent target.
Reporting by Trevor Hunnicutt; Editing by Bernadette Baum and Susan Thomas