U.S. stock futures extended gains on Tuesday as quarterly results from companies including chemical manufacturer DuPont Co. fueled optimism about corporate profit growth despite near-record oil prices.

Dow component DuPont, the second-largest U.S. chemicals maker, posted lower first-quarter income, but its results handily beat analysts' expectations.

Lockheed Martin Corp., the No. 1 defense contractor, posted a greater-than-expected increase in quarterly profit.

Oil prices edged higher in early trading amid strong demand from China and renewed worries over Iran's nuclear ambitions. U.S. June crude futures were trading 40 cents higher at $73.73 a barrel.

After the market opens, investors will pore over reports on existing homes sales and consumer confidence for signs on whether the economy is heating up.

S&P 500 futures were up 2 points, well above fair value, a mathematical formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract.

Dow Jones industrial average futures were up 18 points and Nasdaq 100 futures were up 2.5 points.

The confluence of three themes today -- energy prices, earnings and economic numbers -- should make for an interesting market, said Andre Bakhos, president of Princeton Financial Group in Princeton, New Jersey.

If we have a clear slowdown, the market is going to say (the Federal Reserve) may indeed stop those rate hikes, he said. However, housing has been a very clear driver of the economy, and if housing slumps too much, it could start to affect corporate profits and consumer sentiment, and that's not going to be good.

The Conference Board is scheduled to release April consumer confidence, with economists forecasting a median reading of 106.0 compared with 107.2 in March. The National Association of Realtors (NAR) will release existing home sales for March, with economists forecasting a median 6.70 million annualized unit total versus 6.91 million annualized units in February. Both reports are expected at 10 a.m. (1400 GMT).

In other earnings news, appliance maker Whirlpool Corp. posted stronger-than-expected quarterly profit on demand for new products.

As of late Monday, 69 percent of the Standard & Poor's companies that reported results so far this period came in above expectations, while about 17 percent were in-line and 14 percent missed estimates.

Shares of Sun Microsystems Inc. climbed in early trading on the Inet electronic brokerage network. The computer maker late Monday posted a net loss but said revenue rose and announced that Jonathan Schwartz will replace Scott McNealy as chief executive. Sun shares gained 8 percent to $5.38.

Shares of Netflix Inc. rose after the closing bell on Monday after the online DVD rental company said it turned in a larger-than-expected profit after posting a loss in the same period a year ago. Netflix shares were up 5.6 percent to $33 on Inet.

After the bell, online retailer Amazon.com Inc. is expected to report results.