The architect of the new National Stadium has said his team is remedying the nation's latest Olympic blunder: nowhere for the Olympic flame to burn.

Kengo Kuma said work is underway to find space for a cauldron that traditionally burns during the tournament, adding that it may be necessary to lift fire restrictions for the event.

Kuma's design, adopted in December, replaced a previous effort that was junked on cost. It lacked provision for a cauldron because there was no mention of it in a government development plan in August.

The IOC stipulates that the cauldron should be ideally placed somewhere visible both from inside and outside the stadium.

"The reviewing team is already working on it, and once the direction is there, I'll deal with it accordingly," Kuma said during a speech Wednesday at the Japan National Press Club. "There are various methods (to set it up), so there's no need to worry."

Kuma said the placement of a cauldron was not on the agenda during the December bidding. His design incorporates much wood, including stands covered by wood materials.

He played down fears that the cauldron could fall foul of the Japanese Fire Service Act.

"I didn't propose it at the bidding because it wasn't requested, but I thought it was highly likely to be placed inside the stadium, looking at the London Olympics, for instance."

"The edge of the roof is made of iron, so a fire will not spread. Either way we'll be requesting to lift the restriction (of the law) on condition of placing it in a safe location. We're simulating various possibilities."