Postecoglou ended his tenure as national coach after taking up the role four years ago.

Speculation regarding his future has been rife since October after rumours swirled he could walk away.

And the mentor only added fuel to the fire after refusing to confirm his intentions on whether he would continue coaching Australia.

That speculation was put to bed in Sydney Wednesday morning when Postecoglou resigned from his post.   

“It’s been the toughest decision, it’s not the ending I envisaged,’’ Postecoglou said.

“There wasn’t really a tipping point. It’s something I’ve mulled over for a while, I guess it’s just the nature of me as a person.

“I really tried to coach for the moment, knowing there’s the possibility it could end any time. I’ll always have a sense of unfinished business, I think that would have happened whenever I left.”

Postecoglou has copped considerable flak from past players and the football public alike on the back of the Socceroos' long route to World Cup qualification.

He admitted the job had taken a toll.  

“I’m just so invested in football in this country, whatever role I’ve had in or out of the game, football will always be dear to me and my major driver. I’ll always think I could do something more,” he said.

“Overall, sometimes it’s just an instinct that I just think it’s the right time for me and (FFA).

“It’s been all encompassing. It hasn’t just been coaching the national team — the bit I dearly love is the coaching.”