Mr. Infantino, a close ally of Mr. Trump, said that he met with the American president on Tuesday evening to discuss broader preparations for tournament, which is scheduled to start in under 100 days, with 48 teams playing across three countries. Mr. Trump, as part of that discussion, “reiterated that the Iranian team is, of course, welcome to compete in the tournament in the United States,” Mr. Infantino said in a social media post.