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* China seeks WTO backing to impose sanctions on U.S.
* Apple gains ahead of expected new iPhone launches
* Energy stocks gain along with crude oil prices
* Western Digital, Seagate, Micron drop on price worries
* Indexes up: Dow 0.27 pct, S&P 0.20 pct, Nasdaq 0.29 pct (Changes comments, updates prices)
By Shreyashi Sanyal
Sept 11 (Reuters) - U.S. stocks rose on Tuesday, boosted by energy companies and technology stocks, including Apple, although there were lingering concerns about the U.S. trade war with China.
The markets shook off a weak start to the session and by mid-morning seven of the 11 major S&P sectors were trading higher.
While the telecommunications sector's 1.06 percent jump was the biggest, the technology sector's 0.43 percent rise was giving the biggest push to the S&P 500.
Apple rose 1.5 percent, a day ahead of an highly anticipated event at which the company is expected to unveil new iPhone models. UBS forecast Apple's service revenue would grow 20 percent over the next two years.
"Technology stocks are rallying with some positive catalysts like the Apple event coming up," said Cliff Hodge, director of investments at Cornerstone Wealth in Charlotte North Carolina.
"The sectors which have been the natural leaders, like tech, are catching a bid this morning, with some lift from energy stocks that will help buoy the markets."
The energy index was up 0.70 percent, boosted by a jump in oil prices as U.S. sanctions squeezed Iranian crude exports, tightening global supply.
But, trade worries continued to linger.
China said it would approach the World Trade Organization next week for permission to slap sanctions on the United States due to its non-compliance with a ruling in a dispute over U.S. dumping duties.
The move follows President Donald Trump's threat on Friday to slap tariffs on nearly all Chinese imports.
"It seems like markets are taking a wait-and-watch approach to assess how these trade negotiations are going to turn out."
At 11:39 a.m. ET the Dow Jones Industrial Average was up 69.95 points, or 0.27 percent, at 25,927.02, the S&P 500 was up 5.86 points, or 0.20 percent, at 2,882.99 and the Nasdaq Composite was up 22.66 points, or 0.29 percent, at 7,946.82.
Shares of companies such as Home Depot and Lowe's rose more than 1 percent to hit record highs for the second straight day as retailers could see a boost in sales in the aftermath of Hurricane Florence. The storm was upgraded to Category 4 ahead of landfall on Thursday.
Generator maker Generac was up 1.6 percent.
Activision Blizzard rose 5.3 percent, the most on the S&P, and Take-Two Interactive gained 2.4 percent after brokerage Stifel forecast a strong reception for their games in the holiday period.
Western Digital fell for the ninth straight session, sliding 4.1 percent on Tuesday after RBC echoed other brokerages in warning that falling NAND chip prices would hit the company.
Rival Seagate dropped 3.6 percent and chipmaker Micron fell 3.9 percent, and along with Western Digital were the top losers on the S&P.
Advancing issues outnumbered decliners by a 1.04-to-1 ratio on the NYSE, but declining issues outnumbered advancers for a 1.25-to-1 ratio on the Nasdaq.
The S&P index recorded 25 new 52-week highs and 14 new lows, while the Nasdaq recorded 67 new highs and 77 new lows. (Reporting by Shreyashi Sanyal in Bengaluru; Editing by Arun Koyyur)