GHENT, Belgium (AP) _ Lennart Johansson of Sweden opened his campaign to head soccer's world governing body, FIFA, today and his backers called on secretary general Sepp Blatter to resign immediately if he plans to challenge the Swede.

Johansson, who heads the European soccer federation, is the only declared candidate so far, but outgoing president Joao Havelange has publicly backed Blatter to be his successor. Blatter has yet to make a public move.

``If there is a candidate anywhere else in the world, it's time to show up,'' said Johansson. The deadline for declaring is April 7 and the election June 8, two days before the opening of the World Cup.

As president of the European federation, Johansson chose the preliminary draw of the 2000 European Championships this weekend to announce his bid. In addition to backing from his European group, he produced messages of support from the heads of the Asian, African and Oceania federations and the IOC.

Highlighting his long opposition to Havelange's 24-year rule, which he has called autocratic, Johansson said in his election platform he will aim ``to strengthen the democratic spirit and establish a fair and accountable system'' at FIFA.