NEW YORK (Reuters) - U.S. stocks fell in choppy trading on Monday, with traders nervously eyeing the start of earnings season, while the S&P 500 failed to remain above a key technical level.

With top economic indicators, including payrolls, out of the way, equities had little in the way of catalysts. The recent strength in the U.S. dollar and continued weakness in the European economy cast a shadow over the earnings season that is about to begin.

"Markets are reflecting nervousness around third-quarter earnings given the strong dollar and a very weak macro environment in Europe," said Jim Russell, senior equity strategist for U.S. Bank Wealth Management. "It is very possible that estimate cuts are in front of us,"he said.

Micron shares fell 4 per cent to US$32.57 after Samsung unveiled plans to spend US$14.7 billion on a new semiconductor facility.

Hewlett-Packard posted the S&P 500's largest gains, up 4.7 per cent to US$36.87 after it said it would split into two listed companies and eliminate another 5,000 jobs.

The Dow Jones industrial average fell 17.78 points, or 0.1 per cent, to 16,991.91, the S&P 500 lost 3.08 points, or 0.16 per cent, to 1,964.82 and the Nasdaq Composite dropped 20.82 points, or 0.47 per cent, to 4,454.80.

The S&P 500 was unable to hold above 1,975, "which is proving to be a real resistance point," said Ken Polcari, director of the NYSE floor division at O'Neil Securities in New York.

The benchmark's 50-day moving average stands just below 1,975 and it has closed below that average for five straight sessions.