Stock index futures fell on Tuesday, putting the S&P 500 on track for a third straight decline, on renewed fears the euro zone's sovereign debt crisis was worsening and tracking European stocks.

European shares fell for a third straight session early Tuesday, led by euro zone banks as rising debt yields and an increasingly fractious political backdrop to the region's debt crisis continued to spook investors.

The region's stocks tumbled 4 percent Monday, with financial issues falling to their lowest in more than two years. U.S. markets were closed for the Labor Day holiday on Monday.

Swiss shares bucked the trend, boosted after Switzerland's central bank intervened to drive down the value of the franc, buoying exporter shares such as Transocean Ltd.

Asian equities fell Tuesday on fears that Europe could trigger a second full-blown banking crisis.

Market concerns have resurfaced regarding the euro debt struggles and global economic stability. This is driving fear among investors and bringing an atmosphere of reduced equity exposure, said Andre Bakhos, director of market analytics at Lek Securities in New York.

These concerns have not left the market, they have only been diverted by a lack of headline prominence, and now they are coming back to start the negative cycle all over again.

S&P 500 futures lost 23.7 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 200 points, and Nasdaq 100 futures dropped 34.25 points.

Investors awaited the Institute for Supply Management's August non-manufacturing index at 10:00 a.m. EDT for insight into the pace of economic recovery. Wall Street expectations are for a reading of 51 versus the 52.7 in the prior month. Data on Friday showed zero net U.S. employment growth and stoked recession concerns.

Big U.S. banks, in talks with state officials on settling claims of improper mortgage practices, have been offered a deal that could limit legal liability in return for a multibillion-dollar payment, the Financial Times reported.

Bank of America Corp lost 4.6 percent to $6.92 and JPMorgan Chase & Co fell 2.4 percent to $33.80 in premarket trade.

Sunoco Inc, which has been shedding assets to focus on its logistics operations, plans to exit its refining business.

Dell Inc is partnering with China's top search engine Baidu Inc to develop tablet computers and mobile phones, targeting the Chinese market dominated by Apple Inc and Lenovo Group Ltd devices.

(Reporting by Chuck Mikolajczak; editing by Jeffrey Benkoe)