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 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.

The question becomes, 'Does Sunday night's announcement create a moral hazard where governments are really not going to take the extreme steps they have to?' said Paul Mendelsohn, chief investment strategist at Windham Financial Services in Charlotte, Vermont.

You're trying to solve debt with debt. That's not really a great prescription for a long term solution.

Data that showed Chinese annual inflation pushed up to an 18-month high in April added to the morning's negative tone as it raised the possibility of higher interest rates in coming months. The data, as well as the stronger U.S. dollar, weighed on commodity prices, which could pressure shares of resource companies.

In the United States, wholesale trade data for March is expected at 10:00 a.m. Wholesale inventories are expected to rise 0.5 percent compared to 0.6 percent the previous month, while wholesale sales are expected to rise 1 percent from 0.8 percent the month before.

S&P 500 futures fell 13.3 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 113 points, and Nasdaq 100 futures lost 22.25 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.

(Editing by Padraic Cassidy)