July 1 (Reuters) - U.S. stock index futures slipped on Wednesday, kicking off the second half of 2026 cautiously amid fresh doubts over peace in the Middle East, while investors awaited commentary from Federal Reserve Chair Kevin Warsh.

Tehran said it would not meet with top U.S. envoys who flew to the region following ​an outbreak of hostilities, suggesting that a breakthrough in peace negotiations was not imminent.

Repeated false dawns in negotiations have made the war situation difficult to track, leading some investors to focus instead on the underlying pillars of the economy.

But the declines on Wednesday indicate that the U.S.-Iran war remains difficult to ignore, especially given the impact the Middle East has on the global energy markets.

At 5:20 a.m. ET, Dow E-minis were down 137 points, or 0.26%, S&P 500 E-minis fell 22.5 points, or 0.3%, and Nasdaq 100 E-minis slipped 166.25 points, or 0.54%.

Investors are also worried that the Federal Reserve may need to hike rates and keep them elevated to keep inflation under control.

Traders expect the central bank to raise rates at least once by the end of the year, according to data compiled by LSEG.

Additionally, data released on Tuesday showed that U.S. job openings edged up to a two-year high in May, indicating that the labor market remains stable. That could give the Fed less reason to worry about employment and allow it more room to focus on keeping prices stable.

"The markets will increasingly home in on U.S. interest rate risk. The data is pointing in a direction that suggests employment is no longer an impediment to the Fed in tackling inflation and possibly raising rates," said Kyle Rodda, senior financial market analyst at Capital.com.

Rate uncertainty is also high because Warsh, who took over as Fed chief in May, has launched a review that could reshape how the central bank communicates with the public.

In his first policy meeting as chair, he organized a consensus ​around a policy statement that jettisoned any forward guidance on what actions the central bank might take in the near term.

Warsh will join other central bank chiefs at a forum in Portugal later on Wednesday. Traders will also parse U.S. manufacturing activity data from the Institute for Supply Management, due later on Wednesday.

Major stock movers in the premarket session included Nike, which fell 3.5% following results, as the sportswear giant signaled that its turnaround strategy still faces obstacles.

Shutterstock dropped 28.3% after calling off its planned merger with Getty Images.

(Reporting by Niket Nishant in Bengaluru; Editing by Joyjeet Das)