Arnold fears for the future, alarmed at a lack of junior development as the sport in Australia trails in the wake of cashed-up Asian nations.

"The Socceroos are just the icing on the cake," Arnold told reporters.

"And whatever that icing, whether it tastes good or bad, the most important thing is the ingredients.

"The ingredient is junior development, junior national teams.

"If that's not right, the icing will not taste very good."

Arnold could coach the Socceroos for the last time in their World Cup clash against Denmark on Wednesday (0200 AEDT Thursday).

But even if the Socceroos win and advance to the knockout stages of the cup for just the second time, deep-seated issues remain for Football Australia, he said.

"Whatever happens with this World Cup, I think the organisation needs a review of what is going on in junior development," he said.

Arnold's tenure as Australia's coach started after the 2018 World Cup in Russia - he attended the tournament and was immediately concerned.

"I could see straight away that (Tim) Cahill, (Mile) Jedinak, (Mark) Milligan, (Robbie) Kruse, an ageing squad was there," he said.

"I had already taken the job. I needed to find players.

"And when I started looking, there was nothing coming through.

"When you're ringing A-League coaches and you're talking about two players per club ... it's not right.

"We need more kids given an opportunity in Australia.

"For me, there is massive concern for the future unless it's fixed."

Arnold took on the job as coach of Australia's under 23 side in addition to the Socceroos as a "quick fix" talent search.

"That's why I did the Olympic team for nothing, that's why I had to do it," he said.

"When I asked the organisation 'what is the Olympic program?', and it's 10 days preparation with a team that didn't have a coach two months before, those type of things are not right."

Arnold wanted his legacy to be an improved status of football in Australia.

"Football in Australia is probably the fourth or fifth main sport after AFL, rugby league, rugby union, cricket ... then there's football - they call it soccer, it's football," he said.

"So to leave a legacy is huge.

"It's about putting the game on the map a bit more in Australia but there's so much more work to do and to look at."

Asked what should be a first priority, Arnold replied: "Hire about 150 people.

"The game is growing and growing. Asia is growing so quickly.

"People can sit back at home and their opinion is maybe Saudi (Arabia) is not that good or Japan.

"Look at what they have done (in Qatar) - beaten Argentina, beaten Germany.

"Asia is throwing a lot of money into football and we need to catch up."

Australian Associated Press