* Indexes off: Dow 0.03 pct, S&P 0.2 pct, Nasdaq 0.1 pct (Updates to early afternoon trading, changes byline)
By Caroline Valetkevitch
NEW YORK, Oct 27 (Reuters) - U.S. stocks were slightly lower in early afternoon trading on Monday, led by a drop in energy shares as oil prices extended recent declines.
Shares of Gilead Sciences, up 1.7 percent, helped to limit some of the declines, along with Micron Technology , which jumped 3.5 percent after it announced a $1 billion stock repurchase.
But the S&P 500 energy index, down 2.1 percent, was the biggest negative influence on the benchmark index, with U.S. crude briefly trading below $80 a barrel. Goldman Sachs slashed its crude price forecasts, citing abundant supply and lackluster demand.
"We did have a big run last week, so the fact that we're flattish today is not a surprise," said Bucky Hellwig, senior vice president at BB&T Wealth Management in Birmingham, Alabama.
"There's continued focus on the price of oil, and the debate is, yes, it really helps the consumer... But, in terms of the producers, it's certainly a headwind to say the least."
The S&P 500 posted its best weekly percentage gain Friday since January 2013.
At 1:40 p.m., the Dow Jones industrial average fell 4.33 points, or 0.03 percent, to 16,801.08, the S&P 500 lost 4.11 points, or 0.21 percent, to 1,960.47 and the Nasdaq Composite dropped 4.20 points, or 0.09 percent, to 4,479.52.
The largest percentage gainer on the S&P 500 was Juniper Networks, which rose 3.5 percent, while the largest decliner was Halliburton, down 6.7 percent.
Micron was the largest gainer on the Nasdaq 100, while the largest decliner was Tesla Motors, down 5.5 percent.
Shares of Brazilian companies traded in the United States tumbled after President Dilma Rousseff won reelection in a runoff vote, defeating centrist and market favorite Aecio Neves by a slim margin. Petrobras ADRs slumped 13 percent and Vale lost 5.5 percent.
A Brazilian exchange-traded fund dropped 4 percent.
Declining issues outnumbered advancing ones on the NYSE by 1,883 to 1,092, for a 1.72-to-1 ratio on the downside; on the Nasdaq, 1,563 issues fell and 1,043 advanced for a 1.50-to-1 ratio favoring decliners.
The benchmark S&P 500 index was posting 52 new 52-week highs and one new low; the Nasdaq Composite was recording 36 new highs and 54 new lows. (Additional reporting by Rodrigo Campos, Editing by Bernadette Baum and Meredith Mazzilli)