Formula One ringmaster Bernie Ecclestone has warned the Australian Grand Prix is the "least viable" race on the calendar and could be under threat if it does not become a night event.
The sport has a deal with Melbourne until 2015 but beyond that it is up in the air, with others cities lining up to take its place, he said.
"We have a contract which we will respect -- so up until 2015 we are in good shape," Ecclestone was quoted as saying Thursday by Fairfax Media ahead of Melbourne hosting the opening race of the season on March 18.
"After then, we really don't know. If we were to have a divorce from our friends in Melbourne we would probably be walking away from Australia.
"Because I can't see how Adelaide could make it happen, or anywhere else, if Melbourne can't. The race itself, from our point of view, is probably the least viable of all the races we have."
Last year's Grand Prix cost taxpayers Aus$50 million (US$53.6 million) -- more than the revenue it generates -- with at least AUS$25 million of that reportedly going to Ecclestone for the right to host the contest.
Negotiations for a new contract are expected to begin in late 2013 or early 2014 and Ecclestone said with other countries keen to replace Australia, a night race would go a long way to helping save it.
"I wish we could have a night race in Australia," he said. "We have other races ready to take the place of Australia, which we don't want to happen.
"But it would be wrong of me to have to report to our board, 'Terribly sorry about this but we have to walk away from wherever to retain Australia'."
Ecclestone is keen on a night race so it can be watched at a suitable time in Europe, which would help selling television rights to a continent where the sport is hugely popular.
But it is likely to be opposed by residents who live around the Albert Park circuit, as well as costing the Victorian state government more to stage.
Ecclestone suggested changing to a night race could allow more flexibility in the terms with the state government. "We would have a look, maybe we could help subsidise that a little bit," he said.