Football Federation Australia (FFA) chief executive Ben Buckley has refused to guarantee the A-League will expand beyond eight teams by its fourth year.
Buckley confirmed talks on the A-League's future direction would start immediately the current season was finished.
But former AFL executive Buckley, who took over the FFA top job late last year, has set the bar high for any would-be newcomers to the competition.
He said expansion clubs would have to prove they were capable of being an immediate force on and off the field.
And he warned the timing would have to be right before new clubs were admitted - and that may not be by 2008-09 as had been previously mooted.
Buckley said the FFA could take up to 12 months to formalise a future plan for the A-League.
"We'll be looking at where we want to be over the long-term, how many teams, where they should be located, and part of that is timing," Buckley said.
"It's too early to say specifically how many teams is the right number.
"We've got to look at the growth of population centres, where there's strong interest levels and participation levels, the viability of clubs if they were introduced into certain areas.
"That's a lot of work that needs to be done over the next six to 12 months."
Well-organised consortia in Townsville and Wollongong have expressed strong interest in joining the A-League as soon as possible.
Canberra and the Gold Coast have also been mooted as possible expansion zones.
But Buckley said those clubs which entered the league would be expected to hit the ground running, rather than be allowed to gradually find their feet.
"One of the key issues is making sure the clubs when they come into the competition can be competitive on the field and financially stable off the field," Buckley said.
"We want to make sure they play out of first-class venues and attract average attendances upwards of 15,000.
"They're some of the criteria we need to measure them against."
Already two existing A-League clubs are without owners - Perth Glory and New Zealand Knights - with the FFA controlling both while new backers are found.
Buckley said negotiations were underway with a possible buyer for the Glory.
He was also hopeful the Knights, whose previous owners had their licence stripped by the FFA, would survive into next season.
Buckley and FFA head of operations Matt Carroll met the two interested consortia - one based in Auckland and a combined Wellington-Manawatu bid - in New Zealand last week.
"We're very hopeful. All had very strong proposals, but they need some work," Buckley said.
"We've asked them to come back to us in the next two weeks."
The FFA board is expected to decide the Knights' future later this month.