U.S. stock index futures were lower on Tuesday, easing after the previous session's hefty gains and as concerns lingered about how Greece will get its budget deficit under control.

* Stocks racked up their biggest one-day gain in more than a year on Monday as an agreement on a $1 trillion emergency rescue package from the European Union quelled fears a new credit crisis would derail European economies.

* But the International Monetary Fund said on Tuesday that while Greece's public debt is sustainable over the medium term, persistent low growth, or even a moderate economic jolt, could set back the country.

* Resource shares could come under pressure as oil and metals prices fell and the U.S. dollar strengthened and after Chinese inflation edged up to an 18-month high in April.

* In the United States, wholesale trade data for March is expected at 10:00 a.m. (1500 GMT)

* S&P 500 futures fell 13.5 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 tumbled 99 points, and Nasdaq 100 futures lost 24 points.

* Two key amendments to the U.S. Senate's far-reaching Wall Street overhaul bill are expected to be voted on, with a measure that would allow limited oversight of the Federal Reserve expected to pass.

* Senior executives from NYSE Euronext , Nasdaq OMX Group Inc and CME Group Inc will testify to a congressional panel on last week's shock sell-off in the stock markets.

* Big oil will be under the spotlight when U.S. lawmakers grill top executives on the drilling rig explosion and oil spill that threatens an environmental catastrophe in the Gulf of Mexico.

(Reporting by Leah Schnurr; Editing by Padraic Cassidy)

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