By Sam Meredith, CNBC–

U.S. stock index futures were slightly lower Wednesday morning, as market participants looked ahead to another deluge of corporate earnings.

At around 02:45 a.m. ET, Dow futures slipped 17 points, indicating a negative open of more than 28 points. Futures on the S&P and Nasdaq were both seen marginally lower.

Market focus is largely attuned to earnings season, after better-than-feared figures from major companies in the previous session helped the Nasdaq and S&P 500 indexes reach record closing highs.

Tuesday’s move toward an all-time closing high comes less than six months after a sharp decline in late December, which led the S&P 500 to its worst annual performance since 2008. But stocks quickly turned around as the Federal Reserve reversed course on monetary policy while the tone around U.S.-China trade talks improved.

Equity markets also received support from rising energy shares on Tuesday, after international benchmark Brent crude jumped to its highest level since Nov. 1.

Oil prices soared after the U.S. announced the end of six months of waivers that allowed Iran’s eight biggest buyers to continue importing limited volumes of Iranian oil.

In corporate news, AT&T, Biogen, Boeing and Caterpillar are among the major companies expected to publish their latest quarterly results before the opening bell.

Facebook, Microsoft, PayPal, Tesla Motors and Visa are all set to release their latest quarterly figures after market close.

— CNBC’s Fred Imbert contributed to this report.