Economic development minister Steven Joyce said the deadline was "challenging".
"It all depends on the process it has to go through for the Resource Management Act consenting process. That depends a fair bit on the design and how it fits into the permitted envelope."
He said the September 2017 date was still the goal.
Mr Joyce said there had been no change in SkyCity's contribution or the Government's concessions.
The contract with the Government shows the gambling concessions take effect when building starts. It also shows the casino company has a lot of room to move the 2017 deadline, with years of grace before it is in breach.
Auckland Council economic development manager Harvey Brookes said staff were working with SkyCity to "help ensure the facility meets Auckland Council's design aspirations".
He said no consent had been sought, and it was not possible to know whether it would have to be publicly notified until the application had been submitted.
Conventions and Incentives New Zealand chief executive Sue Sullivan said bookings for large conventions were made four to five years ahead.
There was "significant interest" in the SkyCity project, but bookings wouldn't come until building started.
"No one will start talking about a venue until they have good, firm dates.
"When they get firm dates, and some have said when the first sod is turned, then they will be out."
A year after signing the contract, SkyCity doesn't have an executive with a permanent responsibility for the project. The "project director" who started last November has recently left. A SkyCity spokeswoman said a new director was being recruited.
She said the company hoped to put a resource consent application in before the end of the year.
"The date of project completion depends on when resource consent is approved. An opening date will become clearer once resource consent has been granted."
For the Herald's full coverage of the Convention Centre case click here
