By Shashwat Chauhan and Kanchana Chakravarty

(Reuters) -U.S. stock index futures were subdued on Wednesday after a sharp rally in the previous session, when cooling tariff tensions buoyed sentiment, as investors awaited AI bellwether Nvidia's upcoming earnings and developments on the global trade front.

Nvidia is expected to report a 66.2% surge in first-quarter revenue, according to data compiled by LSEG. Shares of the chipmaker rose 0.6% in premarket trading ahead of its results, due to be released after markets close.

Traders in the options markets are bracing for industry-wide volatility, with defensive options contracts drawing heavy attention for the VanEck Semiconductor ETF, the largest semiconductor ETF.

At 06:42 a.m. ET, Dow E-minis were down 2 points, or 0%, S&P 500 E-minis rose 4.25 points, or 0.07%, and Nasdaq 100 E-minis added 39 points, or 0.18%.

Most megacap and growth stocks traded marginally higher after Tuesday's surge, with Nvidia and Tesla leading gains.

All three main Wall Street indexes soared in the last session, after U.S. President Donald Trump backed down over the weekend from his 50% tariff threat against the European Union.

The implementation of the tariffs is now delayed until July 9 to allow for negotiations between the White House and the EU.

"We do not expect a smooth path to agreement, and with the S&P 500 now just 4% from its record high in February, we believe further gains this year are likely to be relatively limited," Mark Haefele, chief investment officer at UBS Global Wealth Management, said in a note.

U.S. equities are on track for robust monthly gains, with the S&P 500 as well as the Nasdaq set for their best monthly showing since November 2023, as easing concerns around global trade, upbeat earnings and tame inflation data boosted risk appetite.

The S&P 500 is now about 4% off its record closing high reached on February 19, having plunged as much as 18.9% below that level in the wake of Trump's erratic tariff announcements that have whipsawed markets for much of his second term.

Minutes from the U.S. Federal Reserve's last policy meeting, when the central bank held borrowing costs steady, are slated for release at 2 p.m. ET.

Personal Consumption Expenditure data - the Fed's favored inflation indicator - for April, as well as a second estimate of first-quarter GDP, are scheduled to be released later this week.

New York Fed President John Williams said central banks must "respond relatively strongly" when inflation begins to deviate from their target, given the high uncertainty around the economic impact of U.S. tariffs and trade policy.