Crude oil rocketed nearly 8% on Monday – its best single session since April 2 – after the U.S. struck Iranian military sites and Tehran retaliated against an air base, throwing the region’s fragile ceasefire into doubt.

The energy shock and a jump in Treasury yields stalled the S&P 500’s record run, leaving the benchmark roughly flat while the Dow and small caps slipped.

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While President Donald Trump attempted to calm nerves overnight, reiterating that Tehran wants to make a deal, Iranian state media reported that Tehran had suspended all message exchanges with Washington in protest over attacks in Lebanon.

Energy markets bore the brunt of the standoff.