Accused terrorist associate Talal Alameddine has admitted to his role in connection with the Islamic State-inspired murder of police employee Curtis Cheng, by supplying the fatal weapon.
But terrorism charges against him have been dropped.
Curtis Cheng was shot dead outside Parramatta police headquarters on October 2, 2015, by schoolboy Farhad Jabar, who died shortly afterwards under police gunfire.
Jabar, 15, allegedly obtained the gun from fellow teenager Raban Alou in a concealed section of Parramatta Mosque about 15 minutes before it was used to kill Mr Cheng.
The court was told at Alameddine's committal hearing in May that he and Alou exchanged a dozen phone calls in the 24 hours before the attack, and that they met in a park on the morning it occurred, but the wrong sized gun was bought.
Alameddine, 24, was observed delivering an item to Alou on his bike later the same day.
Alameddine pleaded guilty in the NSW Supreme Court on Friday to possession of a .38 Smith and Wesson special calibre revolver connected with the preparation for a terrorist act, and being reckless as to that connection.
He also pleaded guilty to supplying the revolver to Alou.
However, the Director of Public Prosecutions dropped charges of acquiring a pistol subject to a firearms prohibition order, hindering the discovery of evidence and planning for a terrorist act.???
His trial date has been vacated and he will be given a sentencing date on October 10.
Alou pleaded guilty to one count of engaging in a terrorist act in May.
Two other alleged conspirators, Mustafa Dirani and Milad Atai, will stand trial on June 4.