The U.S. stock index futures point to a lower open Thursday as investors continue to have concerns about the weakening global economy and worsening economic growth momentum.

Futures on the Dow Jones Industrial Average were down 0.21 percent, futures on the Standard & Poor's 500 index were down 0.28 percent and those on the Nasdaq 100 index were down 0.24 percent.

Investors are likely to focus on the Labor Department's weekly U.S. jobless claims data to be reported Thursday. The initial jobless claims report, which measures the number of individuals who filed for unemployment insurance for the first time last week, is expected to fall to 370,000 in the week ending August 25, down from 372,000 in the previous week.

Investors are also likely to focus on the domestic personal spending, as detailed by the Commerce Department's Personal Income and Outlays report, which is expected from the department's Bureau of Economic Analysis Thursday. Personal spending, which measures the change in the inflation adjusted value of all spending by consumers, is expected to show a rise of 0.4 percent in July, up from zero percent in June.

On Wednesday, the U.S. markets made marginal gains as investors continued to maintain a waiting strategy ahead of Federal Reserve Chairman Ben Bernanke's speech at the Jackson Hole symposium later this week in which he is expected to announce monetary easing measures to boost the economy.

The U.S. Bureau of Economic Analysis reported Wednesday the second estimate of the second quarter gross domestic product (GDP), which measures the annualized change in the inflation-adjusted value of all goods and services produced by the economy. According to the report, the U.S. economy expanded 1.7 percent in the second quarter, down from the 1.9 percent rise of the first quarter.

The Dow Jones Industrial Average marginally rose 0.03 percent, the S&P 500 Index was up 0.08 percent and the Nasdaq Composite Index advanced 0.13 percent.

Major European indices were in red as investor sentiment was weighed down by the fear that the economic and financial instability in Spain would worsen the euro zone. It has been reported that Spain's Muncia has asked for a financial assistance of 700 million euros ($845 million) from the Spanish government. London's FTSE 100 was down 18.44 points, Germany's DAX 30 index fell 45.89 points and France's CAC 40 declined 11.18 points.

Asian markets also fell Thursday as investors' concerns about the weakening global economy was revived by the declining Japanese retail sales and disappointing South Korean manufacturers' confidence data.  According to data released by Japan's Ministry of Economy, Trade and Industry, the country's retail sales saw a decline of 0.8 percent in July down from 0.2 percent increase in June.

Meanwhile, according to data released by the Bank of Korea Thursday, South Korean manufacturing BSI Index for September was at 75. A reading below 100 is an indication that the number of firms that see the business conditions deteriorating is more than that of those which see an improvement.