U.S. stock futures pointed to a flat open on Tuesday as investors turned cautious ahead of corporate earnings results, and talk for the need of a second fiscal stimulus package underscored worries about the U.S. economic recovery.

Signaling the economy's difficulty in rebounding from an 18-month-long recession, a member of the Obama administration's economic advisory panel said the United States should plan to possibly provide a second round of stimulus funds to prop up the economy.

Everything right now is waiting for earnings to see how companies are reporting and what guidance they give for the second half of the year, said Dan Greenhaus, market analyst at Miller Tabak & Co in New York.

There's a huge gulf between a reduction in economic contraction and outright growth, and that is something that the equity markets, particularly, are dealing with right now.

Earnings season gets underway this week with Alcoa Inc set to release its quarterly results. Alcoa, the first member of the Dow to report, is expected to post a third consecutive quarterly loss on Wednesday.

S&P 500 futures fell 1.7 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 dropped 17 points and Nasdaq 100 futures fell 1.75 points.

An uptick in the price of oil after four negative sessions could provide support for energy shares, a large component of the S&P 500.

On Monday, the Dow industrials rose and the S&P 500 rebounded in late trading as investors' concerns about the strength of an economic recovery triggered a move into defensive stocks.

The Nasdaq ended lower as investors rotated out of the tech sector, which is viewed as more reliant on the economic cycle.

(Additional reporting by Leah Schnurr and Ellis Mnyandu; Editing by Padraic Cassidy)