'Terrible mistake' to replace FIFA's Infantino - Trump

US President Donald Trump backed FIFA president Gianni Infantino, who is in hot water over allegations of a workplace affair and criticism of a failed private investment scheme.

"FIFA would be making a terrible mistake if, for any reason, they even considered replacing President Gianni Infantino," Mr Trump said in a Truth Social post.

The US president called the Italian-Swiss lawyer "fantastic" and said he "presided over the most successful World Cup, by four times, ever presented."

"If he is gone, it will never be as successful or profitable again!"

Mr Trump's backing of the FIFA president contrasts with the response of US Soccer, which issued a statement critiquing Mr Infantino alongside Canada Soccer and football organisations in Central America and the Caribbean.

Mr Infantino, who faces re-election next March, has denied allegations of wrongdoing, and FIFA for their part has backed its besieged president, calling the backlash "a concerted and ongoing effort by some to undermine" the organisation.

Other football organisations, including the Confederation of African Football and South American governing body CONMEBOL, share Mr Trump's position in supporting the FIFA president.