US STOCKS-Wall St edges lower as early gains dissipate
* Symantec tumbles after CEO firing
* Tensions between Russia and U.S. still in focus
* Nike shares fall after results, Tiffany rises
* Indexes: Dow up 0.09 pct, S&P off 0.18 pct, Nasdaq down 0.87 pct (Updates to mid-afternoon, changes byline)
By Chuck Mikolajczak
NEW YORK, March 21 (Reuters) - U.S. stocks were little changed on Friday, as investors exercised caution heading into the weekend and early gains that pushed the S&P 500 to a record high evaporated.
The S&P 500 lost momentum after hitting an all-time intraday high of 1,883.97, with biotechs among the primary decliners. Biogen Idec Inc, down 8 percent to $319.14, and Gilead Sciences Inc, down 3.7 percent to $72.74, were the biggest drags on the S&P 500. The Nasdaq biotech index fell 3.5 percent.
The Dow and S&P 500 are still on track for their best weekly performance since mid-February.
"We are hitting our heads at the closing highs around the 1875 area. This is the area where you would find some resistance and that seems to be exactly what happened," said Ken Polcari, Director of the NYSE floor division at O'Neil Securities in New York. Continuación...