AFL CHIEF executive Andrew Demetriou has reiterated the League's intent to launch a team in western Sydney in 2012.

In a surprise appearance at the Sydney Swans' season launch on Tuesday, Demetriou said the introduction of a second AFL club in Australia's most populous state had "never been a matter of if, it’s been a matter of when".

He said it would help the Swans win the hearts and minds of local sports fans in their battle against rival codes.

"[The Swans] have been doing the heavy lifting and really admirably, I must say. They’re a fantastic football club and very successful," Demetriou said.

"They’ve got double the turnover of most other clubs in this town. They’ve got easily the highest membership, but it’s tough when you’re competing against 17 other clubs.

"We need another club to put a game every weekend in this market, to have double the number of players so they can help promote the game."

Demetriou said Swans chairman Richard Colless supported the AFL's push into western Sydney and there had been ongoing dialogue between the Swans and the League about the expansion.

However, Swans coach Paul Roos said his club was primarily concerned with ensuring its own long-term viability as a direct competitor entered a market they've called their own for more than 25 years.

"If a second team comes in and we’re not at a stage where we’re almost impregnable, then the whole thing’s going to be a disaster," Roos said.

"I think everyone would agree that you can’t have two bad teams in Sydney … it would set the code back many, many years.

"That’s the part that interests us the most as a club. How we’re going to get to that point by 2012, how we’re going to be as a club, feeling like we are impregnable and we are rock-solid in terms of financial [stability]."

But Demetriou vowed that the AFL’s plans to expand to 18 clubs would not harm the long-term viability of any existing teams.

"Our existing 16 clubs cannot be disadvantaged in any way by this expansion and we’ve made that promise – that our expansion cannot be to the detriment of our clubs and our players," he said.

"If any club … was to get into strife, they know that the AFL’s there to help them. It’s very important for us to have 16 strong football teams."

Demetriou said the League had reassessed its promotional spending in Sydney after just 19,127 people attended the Swans' elimination final against North Melbourne at ANZ Stadium last year.

"That was a good wake-up call again, to reinforce in our minds that we had to continue to invest, to continue to support the Swans and continue to make sure that our spend and where it’s going has to be reassessed," he said.

"The games out at ANZ Stadium have traditionally been very well attended and that final last year, we think, was more of an aberration and not where we’re heading for."