HALIFAX -- A senior official with the Canadian Forces says there's been a slight delay in issuing a complex request to industry for an off-the-shelf design of the country's next generation of warships.

Pat Finn, the assistant deputy minister of materiel, said Thursday the request for proposals for the Canadian surface combatant vessels -- originally expected to be issued this month -- will now be going out before mid-October to allow bidders a last chance to make suggestions on the design criteria.

Finn said during an interview at a conference in Halifax that Defence is working with the prime contractor, Irving Shipbuilding, to produce over 1,500 pages of specifications for the Royal Canadian Navy ships.

The warships will replace the Halifax class frigates and Iroquois class destroyers and may still be steaming off Canadian waters by 2070, said the former navy admiral.

Finn said discussions with suppliers have caused the delay.

"There are areas where I would say some of the bidders are not completely happy with the approach. There are areas where we get diametrically opposed comments and we have to deal with it. But fundamentally it's getting the navy the ships that it needs," he said.

Finn says after the request for proposals is issued, the design bids would come in early in 2017 and by the end of next summer a general design may be selected, though final contracts on detailed designs would be negotiated over several years.

The original construction cost for 15 surface combatant vessels was pegged at $26 billion, but defence sources told The Canadian Press last year that figure is outdated and will go higher, possibly "north of $40 billion."

Finn said he couldn't give an updated figure, and said it may only become precise as the first ships are being produced beginning in the 2020s.

Nailing down costs for projects that extend out for decades is a complex task, he said.

"Think of all the cars you're going to own between now and 2040 and tell me what the price of those cars are going to be?" he said.

The assistant deputy minister said he's pleased with the progress at the Irving shipyard on the first Arctic offshore patrol vessel, which is slated for completion in 2018.

However, Finn also said during a speech that there has "been some slippage" on the schedule for the first ship.

"The first ship will be done in 2018. It's a dynamic of when in 2018. ... It's the learning ship where you're testing every part of the facility," he said.