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Closing numbers are viewed on the floor of the New York Stock Exchange on August 18, 2011. Amid concerns about the US and global economies, stocks fell sharply. At the preliminary close, the Dow Jones industrial average had fallen 418 points, or 3.7%, to close at 10,991.

The concern is that the $172 billion deal may not be enough to keep Greece from eventually defaulting and possibly abandoning the euro.

Dow Jones industrial average futures fell 18 points at 12,927 about 30 minutes before the market opens. The Standard & Poor's 500 gave up 1.2 points to 1,358.90. Nasdaq composite index futures were down 2.5 points at 2588.50.

Investors were cautious about the Greek debt deal, which also requires private sector bondholders to forgive $141 billion in Greek debt by taking a loss on the face value of their bonds and accepting longer repayment periods and lower interest rates. Among the concerns are that the bailout package does not include measures to boost economic growth. The Greek economy is entering its fifth year of recession.

Fitch ratings agency downgraded Greece further into junk status following the bailout deal.

Among the U.S. stocks to watch in Wednesday's session is Toll Brothers Inc., after the luxury homebuilder posted a first-quarter loss, but reported an increased number of signed contracts and backlog, important measures for coming months. CEO Douglas C. Yearley Jr. said the company is starting to see a recovery in certain regions, and "in general the market feels healthier than it did one year ago." Toll Brothers shares dipped about 2.5 percent to $23.10 in premarket trading.

Another closely followed housing barometer, existing home sales, will be released by the National Association of Realtors at 10 a.m. (1500 GMT).

Also expected to draw attention is computer maker Dell Inc., which reported an 18 percent drop in first-quarter profit late Tuesday, hurt by slow sales to government agencies, tough competition from Apple Inc. and flooding in Thailand that disrupted its supply chain. Dell shares lost 6.6 percent to $17 in premarket trading.

Rival Hewlett-Packard reports its results after the market closes on Wednesday.