The government released K10 million earlier from the budgeted K30 million, The National newspaper reports.
A joint supervisory body comprising delegations from PNG and the Autonomous Government of Bougainville met at the weekend.
O'Neill and ABG president Dr John Momis said they were pleased with the outcome as many outstanding issues were discussed to progress the referendum according to the peace agreement.
Speaking during a media conference after signing of the aareement in Port Moresby on Friday, O'Neill said the meeting was constructive as they reaffirmed their commitment to Bougainville.
He said while they concluded a successful dialogue, they also reset the date for the referendum from June 15 to October 12 this year as recommended by the Bougainville Referendum Committee led by chairman Bertie Ahern.
He said writs would be issued in August with voting to take place in October which they want to be free and fair.
The results will be forwarded to Parliament to deliberate on.
O'Neill said the national government would continue to support Bougainville to ensure funding was released and voter registrations were done to include those in Bougainville and outside.
O'Neill said a task force was established comprising officers from both governments to deal with some of the outstanding issues.
He said among the issues was more awareness work, The National reported.
The prime minister welcomed the move taken by the Mekamui faction to surrender weapons.
O'Neill said all weapons should be surrendered to pave the way for the referendum.