Stock index futures fell on Wednesday, extending the previous day's slide, as signs the U.S. economic recovery may be slowing and worries about the euro zone's debt crisis weighed on sentiment.

Recent weak economic data, including soft manufacturing data from the Atlantic region and disappointing New York and Philadelphia Fed manufacturing surveys, pointed to a slowdown in the pace of economic growth.

For more insight into manufacturing, investors will focus on U.S. durable goods orders for April due at 8:30 a.m. (1230 GMT).

Durable goods orders are expected to have dropped 2.2 percent in April, a sharp correction from the gain of 4.1 percent the month. April's performance is likely to be weighed down by weak aircraft orders.

Other data due includes home price numbers due at 10 a.m. (1400 GMT).

The S&P 500 closed at its lowest level in over a month on Tuesday and ended below its 50-day moving average for a second straight day. The Dow fell for the third session in a row.

S&P 500 futures fell 1.1 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 lost 28 points and Nasdaq 100 futures fell 4.5 points.

In earnings news, Costco Wholesale Corp posted a higher quarterly profit as it sold more gasoline and got a boost from stronger foreign currencies.

Other quarterly earnings set for release include Computer Sciences Corp , seen reporting earnings per share of $1.11 against $1.66 a year ago, and Polo Ralph Lauren , seen reporting EPS of 79 cents against $1.14 a year ago.

The U.S. Treasury made a small profit when it sold a portion of its shares in American International Group Inc on Tuesday, but it was unclear how its investment in the beleaguered insurer will ultimately fare. The shares were sold at $29 a piece.

Greece's battle to win support for new austerity measures aimed at bringing its public finances under control and securing the next tranche of bailout funding also weighed on riskier assets.

Finland's parliament approved Portugal's bailout package on Wednesday, with opponents outnumbered by supporters of the 78 billion euro ($110 billion) plan by the European Union and IMF. Finland's parliament, unlike others in the region, has the right to vote on EU requests for bailout funds.

U.S. regulators launched one of the biggest ever crackdowns on oil price manipulation on Tuesday, suing two well-known traders and two trading firms owned by Norwegian billionaire John Fredriksen for allegedly making $50 million by squeezing markets in 2008.

GE Capital is selling its A$5 billion ($5.3 billion) Australia and New Zealand mortgages books to Pepper Homeloans as concerns rise over a softening of the Australian housing market and rising cost of funds.

In economic news, the OECD said global economic recovery is on track, helped by a stronger United States, but threats ranging from high oil prices to European sovereign debt crises could yet combine to create a bout of stagflation.

(Reporting by Angela Moon, Editing by Kenneth Barry)