At the end of the trading day, the broad OMXS index was down 0.3 percent.
Trump wrote at 1 p.m. local time in Sweden on his Truth Social platform that Iran has taken too long in negotiations for a peace agreement, and that they are now "paying the price for it."
Among large companies, Volvo fared worst, down 3.7 percent after flagging rising cost inflation during its capital markets day in Eskilstuna.
Live casino operator Evolution and mobile operator Tele2 went against the trend, up 3.1 and 2.2 percent respectively.
After Trump's statement, the price of oil rose. A barrel of North Sea oil cost just over $92 at 5:30 p.m. local time in Sweden, compared with $91 shortly before.
