In front of a sell-out crowd of 57,226 at Optus Stadium, the Socceroos were outplayed for long periods by an inexperienced Japan side.

But then Riley McGree cut the ball back to defender Behich, who rifled a bullet into the corner for his first international goal in 13 years and trigger scenes of jubilation.

After beating Japan for the first time since 2009, Australia are all but assured of a berth at next year's World Cup in North America.

Before the game the Socceroos had a three-point lead and a significantly better goal difference over Saudi Arabia with two matches left.

The win does not totally guarantee Australia's passage, with Saudi Arabia at Bahrain later on Thursday.

Australia face Saudi Arabia in Jeddah on June 10 in their final Group C match in the battle for second behind Japan.

Teams that finish in the top two of the six-team group guarantee their automatic spot at the World Cup.

After what had been a lacklustre performance for much of the game, Australia's last-gasp victory continued their turnaround since Tony Popovic was installed as coach in September.

After becoming the first team to punch their tickets to the World Cup, Japan coach Hajime Moriyasu used the trip to Australia as an opportunity to experiment with his squad.

Liverpool midfielder Wataru Endo and Real Sociedad's Takefusa Kubo started on the bench as Japan fielded three debutants in the starting line-up.

Crystal Palace's Daichi Kamada, playing his 41st international, was considerably their most experienced starting player.

But Japan's youngsters completely dominated the first-half with 21-year-old wing back Kota Tawaratsumida impressing on debut.

It was only a matter of time before Japan had a clear-cut chance at breaking the deadlock, with Yuito Suzuki making an attempt from long range on the half-hour mark.

Japan continued to attack with debutant Yu Hirakawa firing a bullet just wide of the left post after beating outstretched goalkeeper Mathew Ryan.

The break arrived at an good time for Australia.

After being substituted on in the 64th minute, Kubo curled past the right post, before Behich stepped up late on with his priceless goal.