With attendances up and the Western Sydney Wanderers giving the league a bigger worldwide profile after its AFC Champions League (ACL) success there's a growing demand for a 12-team competition.

However, with Newcastle Jets still up for sale and the Central Coast Mariners struggling financially, Gallop is willing to wait.

"We need to have sustainability and financial viability across the 10-team competition and we don't have a set time that we must expand by," Gallop said.

"But we want to have more than 10 teams. We want to explore linking that with our next broadcast negotiation to maximise our value.

"But the welfare of our current teams and making sure they have their heads above water is part of the timing of expansion."

Question marks also remain over Wellington Phoenix's future participation in the A-League with New Zealand not part of the Asian Football Confederation.

AFC officials in the past have expressed a level of discomfort at having a team from another confederation involved in a league from Asia.

Unlike the other nine clubs, Phoenix's licence was not extended by the FFA last year with its deal expiring at the end of 2016.

Gallop said he was waiting to hear from Phoenix powerbrokers about their plans before a decision will be made.

"We're talking again about the condition of the licence and the ball's in their court," he said. "We'd like to know what their long-term strategy is.

"Let's wait and see what their proposal looks like."

Several regions have expressed interest in joining the A-League - a third Sydney team, a second Queensland side and Wollongong outfit all rumoured to be in contention.

Gallop remained tight-lipped about who's in pole position but said lessons had been learned from the demise of North Queensland Fury and Gold Coast United in 2011 and 2012.

"I've said before we want to fish where the fish are," Gallop said.

"We have to be conscious of areas where there are millions of fans rather than just a few hundred thousand.

"That is not to discount any area. We're currently doing some fresh research across a number of areas.

"I've met with a number of people.

"There's always great enthusiasm, but like most codes in Australia, football has learnt some harsh lessons on expansion in the past.

"We need to hasten slowly to that 12-team competition."