Adelaide United, the hastily assembled side which took last summer's National Soccer League by storm, will take part in the new national competition next year.

The club signed a participation agreement with the Australian Soccer Association (ASA) just days after withdrawing its bid because of a disagreement over the structure of the new league and financial issues.

A compromise with the club's owners, the Pickard Group, was reached during a meeting between ASA chief executive John O'Neill and Pickard Group boss Gordon Pickard, the two brought together by South Australian Premier Mike Rann.

It means Adelaide is now set to join seven other clubs in the new league which is due to start in August.

"We are absolutely over the moon that Adelaide United and the Pickard Group are back on board," O'Neill said.

"It (the new competition) would not have been the same without an Adelaide team."

O'Neill confirmed that four other clubs bidding to join the competition, Brisbane, Newcastle, Gosford and Sydney, were expected to sign on Thursday while a fifth, Auckland, was very close to signing.

Negotiations with Perth and Melbourne were still continuing.

Adelaide's change of heart came after ASA eased its concerns over the structure of the new competition which O'Neill said would be modelled on that used by the Football Association in England and its Premier League.

The two parties resolved differences over access to advertising and corporate facilities at Adelaide's United's home ground, Hindmarsh Stadium.

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