Wirz also said a multi-purpose stadium in London could work, pointing to the success of the Stade de France in Paris, which has hosted international athletics, football and rugby events.
"Keeping the athletics track must be part of any future plans for the Olympic Stadium," Wirz said in a statement.
"London needs a high-quality venue that has the potential to host future European Athletics Championships and World Championships."
A public relations battle is developing over the future of the 496 million pounds stadium after Premier League football club Tottenham Hotspur said they planned to largely demolish the venue and replace it with a purpose-built soccer ground after the Games if they are chosen as anchor tenants.
A rival bid from fellow Premier League club West Ham United, whose Upton Park ground is just five kilometres from the Olympic Park in Stratford, east London, has widespread support at they plan to leave an athletics and multi-sport legacy.
Leading athletics figures have warned that failure to retain a track could have far-reaching implications for Britain's standing in world sport.
The overriding concern of politicians is that the stadium can pay its way and does not turn into a "white elephant".
Final bids need to be made in the coming days, with the Olympic Park Legacy Company (OPLC) due to choose its preferred option at the end of the month. It will then be up to the government and the Mayor of London to decide.
Tottenham, who outlined the details of their bid for a 60,000-seater stadium last week, have already gained planning approval to build a new stadium on the site of their current home in north London but a move to Stratford is considered more cost-effective.
To fulfill the athletics legacy obligation, they would refurbish the National Sports Centre (NSC) in Crystal Palace, south east London, currently a 15,000-seat athletics stadium used to host the annual London Grand Prix meeting.
The BBC said on its website that Championship club Crystal Palace were reported to be planning a move to the NSC from their nearby home at Selhurst Park.
IOC chief Jacques Rogge has distanced himself from the stadium debate but said last week he "would favour a track legacy", while London organising committee (LOCOG) chairman Sebastian Coe is also backing West Ham's proposals.
