Stock index futures were mixed on Wednesday, pressured by rising bond yields and a stronger dollar.

Yields rose along with the greenback following Tuesday's deal to extend tax cuts that intensified worries about inflation and the costs of the government's debt burden.

Higher bond yields make it more expensive for consumers and businesses to borrow, while stocks and the dollar have moved in opposite directions of late. A rise in yields and the dollar could also draw money away from equities.

The 10-year U.S. Treasury yield rose to 3.25 percent overnight, a level not seen since late June and beyond Tuesday's high of 3.18 percent.

Adding negative sentiment was news the U.S. Securities and Exchange Commission has issued more than a dozen subpoenas in its investigation of insider trading on Wall Street, potentially undermining public confidence in the markets.

The S&P 500 faces resistance at the 1,228 level, which represents the 61.8 percent Fibonacci retracement of the 2007-2009 bear market slide, a key technical indicator. The level was confirmed as strong resistance on Tuesday after the index broke through during the session but closed below that point at 1,223.12.

S&P 500 futures dipped 1.1 points and were below fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures fell 9 points, while Nasdaq 100 futures added 4.25 points.

Bellwether Texas Instruments Inc said it was confident a recent correction in demand for its chips would be short-lived, and also narrowed its earnings outlook in line with estimates.

Retailer Costco Wholesale Corp posted a better-than-expected quarterly profit as sales and traffic rose at its U.S. stores and the weakening dollar helped sales overseas.

Fortune Brands Inc , which owns Jim Beam whiskey, Titleist golf balls and faucet maker Moen, plans to split into three companies.

Stocks eked out a small gain Tuesday after an earlier advance as a tax cut deal was derailed by the rising bond yields and reports of the insider-trading probe.

(Reporting by Leah Schnurr; editing by Jeffrey Benkoe)