* S&P 500 on track for seventh straight session of gains
* Apple extends recent decline after unveiling new iPhones
* Obama requests Congress to delay vote on Syria
* Dow up 0.7 pct, S&P up 0.2 pct, Nasdaq off 0.2 pct
By Ryan Vlastelica
NEW YORK, Sept 11 (Reuters) - U.S. stocks were mostly higher on Wednesday, putting the S&P 500 on track for a seventh straight day of gains as a potential military strike against Syria was delayed, further easing geopolitical concerns.
Wall Street showed resilience even as Apple Inc, the largest U.S. publicly traded company by market capitalization, slumped nearly 5 percent a day after it unveiled new iPhone models and prices. The stock was the biggest decliner in the S&P and kept the Nasdaq modestly lower.
Market nervousness over a possible U.S.-led strike against Syria abated as U.S. President Barack Obama, faced with resistance in polls and Congress, said a Russian offer to pressure Syria to place its chemical weapons under international control raised the chances of putting off a strike.
The President also asked Congressional leaders to delay a vote on to authorize military force in order to allow diplomacy to play out.
"The speech lessens some of the macro concerns out there, and as the worst-case scenario around Syria becomes more unlikely, investors are rotating back towards the market," said Eric Teal, chief investment officer at First Citizens Bancshares in Raleigh, North Carolina.
The S&P 500 has risen about 3.3 percent over the past seven sessions, its longest winning streak since July.
Apple shares fell 5 percent to $469.79, extending a steep decline from the previous session. The stock is on track for its worst two-day performance since April 18, and its loss of nearly $23 billion in market capitalization is roughly the total size of Dell.
The tech titan's product announcements on Tuesday disappointed investors who were hoping for a cheaper version of the iPhone or a new product line. Credit Suisse, UBS and Bank of America Merrill Lynch each lowered their rating on the stock.
What was announced "was less than expected from a company that has a reputation for surprising with a killer product or strategy," said Mark Luschini, chief investment strategist at Janney Montgomery Scott in Philadelphia, which manages about $58 billion in assets.
The Dow Jones industrial average was up 104.91 points, or 0.69 percent, at 15,295.97. The Standard & Poor's 500 Index was up 2.62 points, or 0.16 percent, at 1,686.61. The Nasdaq Composite Index was down 5.93 points, or 0.16 percent, at 3,723.09.
Traders looked ahead to the Fed's two-day policy meeting on Sept. 17-18 when a decision is expected to begin to wind down $85 billion a month in bond purchases. That stimulus has been key in buoying the economy and boosting the benchmark S&P 500 index by nearly 18 percent so far this year.
In company news, hardware distributor Synnex Corp jumped 21 percent to $58 a day after it said it will buy IBM Corp's customer-care outsourcing business for $505 million. IBM rose 2.1 percent to $190.58 to lead gains on the Dow industrials.
Texas Instruments edged down 0.4 percent to $40.15 after the No. 3 U.S. chipmaker lowered its third-quarter forecast.
Economic data showed wholesale inventories for July edged up 0.1 percent, less than an expected rise of 0.3 percent, but better than June's 0.2 percent decline.
Harvest Natural Resources Inc surged 27 percent to $5.25 after the oil and gas producer said it was in exclusive talks to sell itself to Argentina's Pluspetrol in a deal valued at about $373 million including debt.