FIFA President Sepp Blatter makes a speech during the opening ceremony of the 65th FIFA Congress in Zurich, Switzerland, May 28, 2015. [Photo/Agencies]

SPONSOR CONCERNS

Adding to the pressure, there were growing concerns about the allegations from major sponsors, many of whom have solidly backed FIFA despite nearly 20 years of bribery and corruption allegations.

German sportswear company Adidas said FIFA should do more to establish transparent compliance standards. Anheuser-Busch InBev, whose Budweiser brand is a sponsor of the 2018 World Cup, said it was closely monitoring developments.

Credit card company Visa Inc urged immediate reforms.

In a strongly worded statement, Visa said: "Our sponsorship has always focused on supporting the teams, enabling a great fan experience, and inspiring communities to come together and celebrate the spirit of competition and personal achievement ... it is important that FIFA makes changes now so that the focus remain on these going forward. Should FIFA fail to do so, we have informed them that we will reassess our sponsorship".

Coca-Cola Co, another sponsor, said the charges had "tarnished the mission and ideals of the FIFA World Cup and we have repeatedly expressed our concerns about these serious allegations".