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July 8 (Reuters) - U.S. stock index futures slid sharply on Wednesday, with Nasdaq futures touching a four-week low after President Donald Trump said a memorandum of understanding aimed at ending the war with Iran was "over", sending oil prices rising.

Speaking in Ankara ahead of a NATO summit in the Turkish capital, the U.S. president said he had no interest in engaging further with Iran, deepening investor concerns over renewed escalation in the Middle East and marking the latest blow to the fragile ceasefire between Washington and Tehran.

Iran's Revolutionary Guards said they had targeted U.S. military sites in Bahrain and Kuwait after the U.S. launched a wave of strikes on Iran. Washington said those strikes were in response to attacks on tankers in the Strait of Hormuz, a critical waterway for global oil shipments.

Oil prices extended gains on Wednesday following Trump's remarks, with Brent crude futures LCOc1 and U.S. West Texas Intermediate crude futures CLc1 both rising more than 5%.

The jump in crude prices lifted energy stocks in premarket trading. Chevron CVX.N rose 2.4%, Exxon Mobil XOM.N gained 3% and ConocoPhillips COP.N advanced 2.2%.

Devon Energy DVN.N climbed 2.5%, while Occidental Petroleum OXY.N, APA Corp APA.O and Diamondback Energy FANG.O were up 2.6%, 4.2% and 2.4%, respectively.

Investors will also focus on the minutes of the U.S. Federal Reserve's June policy meeting, due later in the session, for clues on how policymakers are assessing inflation risks and economic growth.

According to CME's FedWatch tool, markets are currently pricing in at least one rate hike by the end of 2026.

At 04:56 a.m. ET, Dow E-minis YMcv1 fell 620 points, or 1.17%, S&P 500 E-minis EScv1 lost 63.75 points, or 0.84%, and Nasdaq 100 E-minis NQcv1 shed 330 points, or 1.12%.