"The Iran National Soccer Team is welcome to The World Cup, but I really don’t believe it is appropriate that they be there, for their own life and safety," Trump said in a post on Truth Social.
Iran's sports minister said on Wednesday that Iran cannot participate in the World Cup after the U.S. launched airstrikes alongside Israel against Tehran. The attacks triggered a region-wide conflict that has shown no signs of abating.
The 48-team World Cup will be held in the U.S., Canada and Mexico from June 11 to July 19, with Iran scheduled for matches in Los Angeles and Seattle.
An official withdrawal by Iran from the showpiece event, which has not yet happened, would be a first in the modern era and would leave soccer's global governing body FIFA with the urgent task of finding a replacement team.
Iran was the only nation missing from a FIFA planning summit for World Cup participants held last week in Atlanta.
FIFA did not immediately respond to a request for comment. Late last year it awarded Trump - who has campaigned aggressively for the Nobel Peace Prize - its own inaugural peace prize.
Earlier this week, Australia granted humanitarian visas to five Iranian women soccer players after they sought asylum, fearing persecution on their return home for their refusal to sing the national anthem at an Asia Cup match.
Trump had urged Australia's Prime Minister Anthony Albanese to grant asylum to members of the Iranian women's team, saying the US would if Australia did not.