The Socceroos have edged 10-man Syria 2-1 in extra time to progress to the intercontinental World Cup qualifying play-off after a tense stand-off in Sydney.

Who do we play next? The Socceroos play another two-legged home-and-away play-off against CONCACAF's (North and Central America) fourth-best team.

The Socceroos play another two-legged home-and-away play-off against CONCACAF's (North and Central America) fourth-best team. Playing away before a home decider, Australia will face either Panama, Honduras or the United States on November 6 and November 14.

Locked at 1-1 (and 2-2 on aggregate) since early in the first half, Australia had been constantly frustrated throughout regular time, and through much of extra time, before Tim Cahill rolled back the years with a headed winner to put the Socceroos through to a November play-off against North and Central America's fourth-best team.

Robbie Kruse was put through into the area, and with his back to Cahill, twisted around to cross for the 37-year-old to head home in signature fashion for a remarkable half-century of goals in Australian colours.

But the drama was not over as Syria won a late free kick just outside Australia's area with the seconds counting down. Up stepped Omar al Soma, who hit a rasping shot against the post with Mat Ryan beaten.

Syria, a fairytale team in Asia's World Cup qualifying story, were literally inches away from progressing at Australia's expense, even down to 10 men. A goal for al Soma would have levelled the aggregate at 2-2, and put Syria through on the away goals rule.

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But fate smiled on Australia as it awaits the confirmation of its next opponent, with Panama, Honduras and theoretically the United States completing their World Cup campaigns on Wednesday lunch time (AEDT), with Panama currently CONCACAF's fourth-based team when the final whistle blew in Sydney.

"I knew I was going to score, I didn't touch the ball much but in the end I delivered," said Cahill, a veteran of Australia's last three World Cup campaigns.

"That's what I've done my whole life and I'll continue to do it."

The build-up to the match was dominated by news that Aaron Mooy had been demoted to the bench, and things could not have started worse for Australia when al Soma broke with ease through the middle to slot past Ryan, putting Syria ahead in the sixth minute and sending the visiting fans into raptures.

An injury to Brad Smith soon after saw Mooy brought on just a few minutes later, allaying whatever fuss was caused by Ange Postecoglou's selection.

Nerves were settled almost immediately as Mathew Leckie burst brilliantly down the right before hitting an inviting cross for Cahill, who thumped in a headed equaliser for his 49th strike in Australian colours.

Tim Cahill rolled back the years with an extra-time winner to send Australia to the next play-off. ( AP: Rick Rycroft )

Mooy proceeded to link up brilliantly with Tom Rogic and Kruse down the left in an attacking triumvirate, which proceeded to toy with the Syrian defence thanks to some excellent passing combinations.

Those combinations helped put James Troisi into the box to feed Cahill, but his right-footed finish was blocked by a defender's thigh with the goal beckoning.

But both sides struggled to create chances of genuine quality in the second half, as the tense contest petered out to a draw in regulation minutes, sending the decider to extra time.

Substitute forward Nikita Rukavytsya had two golden-edged opportunities to end the tie in extra time.

Put through early in the first added period, his low left-footed drive stung the palms of Syrian keeper Hamid Mido, before a pinpoint cross found him in acres of space, only to volley straight at the keeper from point-blank range.

Syria was reduced to 10 men after Mahmoud al Mawas picked up a second yellow after fouling Kruse on the flanks, leaving the visitors to shut up shop in the hope of frustrating Australia.

It was left to Cahill to grab the headlines yet again as he steered home the header that took Australia to the final stage of a long qualifying road, as a disappointing 42,136-strong crowd breathed a collective sigh of relief.