Somalian referee Omar Abdulkadir Artan in action during the 2024 Africa Cup of Nations match between Mauritania and Algeria, at Stade de la Paix in Bouake, Ivory Coast, Jan. 23, 2024. (AFP-Yonhap) LOS ANGELES (AFP) -- A Somali referee was on Monday dropped from the World Cup after he was denied entry to the United States, reigniting concerns about how Donald Trump's immigration crackdown could disrupt the tournament.Omar Artan was set to be the first match official from Somalia to referee at a World Cup finals, but he was turned back when he arrived at Miami International Airport on Saturday.The United States Customs and Border Protection (CBP) said Artan was denied entry due to "vetting concerns."World soccer's governing body FIFA said it was powerless to influence the decision, which it maintained was the sole preserve of tournament co-hosts the United States, and confirmed that Artan would play no part in the World Cup."FIFA can confirm that match official Omar Abdulkadir Artan will be unable to train and officiate at the FIFA World Cup 2026 after he was denied entry into the United States," a FIFA spokesperson told Agence France-Presse.Somalia is one of several countries on a travel ban list introduced by US President Trump's administration as part of a broader immigration crackdown.Iran's team were spending their first full day at their base camp in Tijuana, Mexico after arriving in the eye of a diplomatic storm after the US -- embroiled in a military conflict with the Islamic republic -- refused to issue visas to 15 of their support staff.Iran coach Amir Ghalenoei complained on Sunday that the process of obtaining visas had delayed his team's arrival by a week.He added: "Usually in these tournaments, before technical matters, ethical and human considerations must be respected -- which I think for us it was not the case."With the big kickoff in Mexico City on Thursday, Mexican President Claudia Sheinbaum vowed to ensure that threatened demonstrations by a teachers' union over demands for salary raises do not disrupt the opening game between her country and South Africa."We are going to guarantee ... that the celebration of the World Cup is well-executed, in peace and tranquility," Sheinbaum said.On June 1, police dispersed protesters with tear gas and rubber bullets near the historic Zocalo square in Mexico City where authorities have erected a massive viewing screen for a World Cup fan zone.Streets surrounding the square are closed off with metal barricades, which Sheinbaum has said are meant to guard against "provocations." As the days ticked down to the start of this expanded World Cup, the 48 teams settled into their base camps.