U.S. stocks were set to open lower Wednesday, following several days of gains that put all three major indexes at the highest levels since early May.

U.S. stock futures were down between 0.1% and 0.4% early Wednesday.

Investors are awaiting the latest round of corporate results, while keeping an eye on news from Europe and the world's central banks.

Firms including Macy's and Polo Ralph Lauren are scheduled to report their quarterly results before the bell, while News Corp reports will report in the afternoon.

About 85% of the companies in the S&P 500 have reported their quarterly results, and earnings are on pace to grow just 0.6% -- the slowest pace since the third quarter of 2009.

On the bright side, 64% of the companies that have reported so far have topped Wall Street expectations, higher than the average rate of 62% over the past decade.

The government will also release data on second-quarter productivity in the morning.

U.S. stocks rose Tuesday, extending gains for a third day, amid hopes that global central banks will step in to support the market.

In particular, investors are hoping that the Federal Reserve will launch a new round of its asset-purchasing program known as quantitative easing. Some analysts, however, are skeptical that this alone is enough to rejuvenate the sputtering U.S. economy.

In Europe, meanwhile, bond yields for Italy and Spain remain at worrying levels, with Spain in particular potentially in need of additional bailout funds.

World markets: European stocks slid into the red during morning trading. Britain's FTSE 100 and France's CAC 40 fell 0.6%, while the DAX in Germany lost 0.7%.

Asian markets had a mixed finish. The Shanghai Composite rose 0.2% and Japan's Nikkei added 0.9%, while the Hang Seng in Hong Kong dipped slightly.

Economy: At 8:30 a.m. ET, the Bureau of Labor Statistics will release its data on second-quarter productivity, which is expected to have increased by 1.5%, according to a survey of analysts by

Companies: Macy's is expected to post quarterly earnings of 64 cents a share on $6.1 billion in revenue, according to a survey of analysts by Thomson Reuters.

Ralph Lauren is tipped to report earnings of $1.78 a share on $1.6 billion in revenue.

After the bell, News Corp is expected to report earnings of 32 cents a share on $8.7 billion in revenue.

Late Tuesday, Disney reported quarterly results that beat earnings expectations but missed on revenue.

Currencies and commodities: The dollar rose against the euro, was flat versus the British pound, and declined against the Japanese yen.

Oil for September delivery fell 58 cents to $93.08 a barrel.

Gold futures for August delivery fell $2.10 to $1,607.60 an ounce.

Bonds: The price on the benchmark 10-year U.S. Treasury rose, pushing the yield down to 1.61%% from 1.63% late Tuesday.