U.S. stock index futures fell on Tuesday after a broad rally in the previous that took the S&P 500 to its best day in two months as investors fretted over whether Greece could make deep spending cuts.

Drugmakers will be in view after both Merck & Co Inc and Pfizer Inc reported better-than-expected first-quarter profits.

Striking public workers challenged the Greek government's bailout-for-austerity deal with the European Union and the International Monetary Fund as investors fretted about Athens' ability to enforce deeper spending cuts.

Other major companies set to report include News Corp , MasterCard Inc and NYSE Euronext .

On the macroeconomic front, ICSC/Goldman Sachs releases chain store sales at 7:45 a.m. EDT. In the previous week, sales rose 0.2 percent.

At 8:55 a.m., Redbook reports its Retail Sales Index of department and chain store sales for April versus March. In the prior period, sales dropped 2.0 percent.

At 10 a.m., the Commerce Dept releases March factory orders. Economists in a Reuters survey expect a drop of 0.1 percent, compared with an 0.6 percent rise in February. At the same time, the National Association of Realtors will issue March pending home sales. Economists expect a rise of 4.0 percent rise versus an increase of 8.2 percent in February.

S&P 500 futures were down 7.1 points and 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 45 points, while Nasdaq 100 futures dipped 11.5 points.

The financial sector will be in view as the U.S. Senate is set to cast its first votes on a sweeping Wall Street reform bill, with passage of a handful of uncontroversial amendments expected and a key procedural question still unsettled.

Energy shares may be in play as the massive oil spill in the Gulf of Mexico worsens, as BP Plc said it made progress toward capping the underwater well that ruptured almost two weeks ago.

On the M&A front, Silver Lake and Warburg Pincus will buy Interactive Data Corp , the financial data provider, for $3.4 billion in cash.

(Reporting by Angela Moon; editing by Jeffrey Benkoe)