U.S. stock index futures point to a slightly lower open Tuesday ahead of the release of the Labor Department's import and export price indexes scheduled for release at 8:30 a.m. ET.

Futures on the Dow Jones Industrial Average were down 0.02 percent while those on the Standard & Poor's 500 were up 0.1 percent and those on the Nasdaq Composite Index were down 0.02 percent. 

The Labor Department, on Tuesday, will report the import and export price indexes, which measure the average change in the price of goods and services that are traded between the U.S. and rest of the world. Import prices are expected to remain little changed in April from the 0.5 percent decline registered in March while export prices are estimated to dip by 0.2 percent.

The Small Business Optimism Index, released by the National Federation of Independent Business (NFIB), beat expectations and rose to a six-month high of 92.1. The index, which is a composite of 10 seasonally-adjusted components and measures the health of small businesses in the U.S., was expected to nudge up to 89.8 in April, from 89.5 in March.

But, the high reading does not point to any significant improvement in sentiment.

"Pessimism abounds within the sector, as still far more of those surveyed expect business conditions to be worse in six months than those who think they will be better," the NFIB noted on its website.

On Monday, U.S. stocks finished mixed as news reports about the Federal Reserve considering an exit strategy for the massive stimulus measures that have been fueling the economy since late 2008 weighed on investor sentiment.

Meanwhile, retail sales edged unexpectedly higher in April, helped by strong car sales and spending on building supplies.

According to the data released on Monday by the U.S. Department of Commerce, retail sales increased 0.1 percent against an analyst poll by Bloomberg of a 0.3 percent decline.

The Dow Jones Industrial Average fell 0.18 percent to close at 15,091.68, the S&P 500 Index was little changed by percent at 1,633.77 and the Nasdaq Composite Index gained 0.06 percent to end at 3438.79.

Most European markets traded in the red on Tuesday as investors await the euro area industrial production figures, one of the key indicators of growth momentum in the region, as well as a report on German investor confidence.

London's FTSE 100 was down 0.11 percent, Germany's DAX-30 index lost 0.28 percent and France's CAC-40 fell 0.45 percent.

Earlier in the day, most Asian markets ended mixed following the recent yen-driven rally in Japanese stocks, which helped the Nikkei on Monday to climb to peaks not seen since January 2008.

Hong Kong’s Hang Seng Index fell 0.26 percent to end at 22,930.28, Japan’s Nikkei closed down 0.16 percent at 14,758.42, while China's Shanghai Composite Index declined 1.11 percent to 2,217.01. South Korea's KOSPI rose to 1,968.83, up 1.03 percent.