* Futures off: Dow 40 pts, S&P 6 pts, Nasdaq 14.25 pts
By Chuck Mikolajczak
NEW YORK, Sept 23 (Reuters) - U.S. stock index futures were moving lower on Tuesday, putting the S&P on track for a third straight decline, as conflict in the Middle East intensified and after the U.S. Treasury moved to curb "tax inversion" deals.
* The United States and Arab allies bombed Syria for the first time on Tuesday, killing dozens of Islamic State fighters and members of a separate al Qaeda-linked group, pursuing a campaign against militants into a war at the heart of the Middle East.
* U.S.-listed shares of Shire, down 5.8 percent to $241.35 and AstraZeneca, off 4.6 percent to $71.25, lost ground in premarket after the Obama administration took several actions late Monday that will reduce the tax benefits available to companies that have done inversion deals, while also making new inversions more difficult to do and potentially less rewarding.
* Shares of AbbVie, which has agreed to a deal to acquire Shire, was down 4.6 percent to $56 before the opening bell.
* Data expected on Tuesday includes the flash September reading on manufacturing from financial data firm Markit at 9:45 a.m. (1345 GMT). Expectations call for a reading in the main purchasing managers' index of 58 versus the final 57.9 in August.
* Salix Pharmaceuticals was trading up 7.8 percent to $172.30 in light premarket trade after a person familiar with the matter said on Monday Allergan Inc has revived discussions to buy Salix.
* Norway's Yara and Chicago-based CF Industries are in talks about a merger of equals that could create a $27 billion global fertilizer producer, rivaling Canada's Potash Corp in size in a fragmented and oversupplied market.
* S&P 500 e-minis were falling 6 points, or 0.3 percent, with 151,091 contracts changing hands.
* Nasdaq 100 e-minis were down 14.25 points, or 0.35 percent, in volume of 23,930 contracts.
* Dow e-minis were down 40 points, or 0.23 percent, with 21,482 contracts changing hands.
Reporting by Chuck Mikolajczak