US stock futures fell as oil surged and President Trump declared that the memorandum of understanding between the US and Iran was "over," raising the likelihood of a reescalation in the Middle East war.

Futures tied to the Dow (YM=F) fell 1%, or nearly 600 points, while contracts on the S&P 500 (ES=F) dropped 0.8%. Nasdaq 100 futures (NQ=F) slipped 1.3% following a down day for US markets.

Markets are digesting a sharp escalation in US-Iran tensions after American forces carried out a "series of powerful strikes" against Iran late Tuesday in response to attacks on three commercial vessels in the Strait of Hormuz.

President Trump, speaking in Ankara ahead of a NATO summit, stated that the US-Iran ceasefire agreement was over amid the flare-up in hostilities. "As far as I'm concerned, it's just a waste of time dealing with them," Trump said of Iran.

Energy markets have been shaken after the Treasury revoked a license that had allowed Iran to export oil globally, adding to concerns over potential supply disruptions. Crude prices climbed more than 5%, with West Texas Intermediate (CL=F) trading above $74 a barrel and Brent (BZ=F) at $78 a barrel.

Attention now shifts to Wednesday afternoon's release of minutes from the Fed's June meeting. Investors will parse the document for clues about policymakers' thinking after the Fed held interest rates steady at its first meeting under Chairman Kevin Warsh.