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* U.S. and Mexico reach trade deal, Canada talks imminent
* Nasdaq and S&P flat after opening at all-time highs
* Best Buy slides on weak online sales, Q3 profit forecast
* Cosmetics firm Coty, chipmaker Xilinx up on broker upgrades (Changes comments, updates prices)
By Shreyashi Sanyal
Aug 28 (Reuters) - U.S. stocks were little changed on Tuesday, with the benchmark S&P 500 and the Nasdaq hovering at all-time highs, a day after the United States and Mexico reached an agreement on an overhaul of the North America Free Trade Agreement (NAFTA).
The two countries agreed on Monday to overhaul NAFTA and U.S. officials expressed optimism a deal could be reached this week.
"The fears of the trade wars have subsided to a certain degree, but I do believe that anything that comes out of this administration needs to be taken with a grain of salt," said Bryan Keller, managing director of Dakota Wealth Management in Palm Beach Gardens, Florida.
The benchmark S&P 500 and the Nasdaq indexes started the session strongly to hit fresh all-time highs, as they did on Monday after the trade deal was announced, before pulling back.
"After the initial surge to the top of the range you tend to get a little bit of a pullback. You catch people taking profits at the all-time highs," said Michael Antonelli, managing director, institutional sales trading at Robert W. Baird in Milwaukee.
At 11:41 a.m. EDT the Dow Jones Industrial Average was up 14.73 points, or 0.06 percent, at 26,064.37, the S&P 500 was down 1.00 points, or 0.03 percent, at 2,895.74 and the Nasdaq Composite was down 0.46 points, or 0.01 percent, at 8,017.44.
Nine of the 11 major S&P 500 sectors were lower, though five of them were down less than 0.1 percent.
The top gainer among the S&P sectors was the real estate sector, with a 0.36 percent increase and the biggest laggard was telecoms, down 0.36 percent.
Best Buy slid 6.9 percent, the most on the S&P, after the electronics retailer's quarterly online sales growth slowed and its current-quarter profit forecast missed estimates.
Coty rose 6.7 percent, the most on the S&P, and Estee Lauder gained 1.3 percent after Morgan Stanley upgraded the shares of the beauty products makers.
Xilinx gained 1.3 percent, after Baird upgraded the chipmaker's shares on a expected ramp-up in 5G-related shipments later this year.
Campbell Soup fell 2 percent after a New York Post report that the soup maker does not plan to sell itself.
Declining issues outnumbered advancers for a 1.27-to-1 ratio on the NYSE and a 1.03-to-1 ratio on the Nasdaq.
The S&P index recorded 39 new 52-week highs and one new low, while the Nasdaq recorded 80 new highs and 11 new lows. (Reporting by Shreyashi Sanyal in Bengaluru; Editing by Shounak Dasgupta)