The Socceroos failed to qualify automatically for next year's finals in Russia after they could only sneak a 2-1 win over Thailand in their final match in Melbourne on Tuesday.
Saudi Arabia then beat Group B winners Japan 1-0 in Jeddah later on Tuesday to clinch the second automatic spot, consigning Australia to the third-placed playoff against Syria.
"We are all disappointed that we did not achieve direct qualification from our group but we are confident we can still make it to Russia," Football Federation Australia Chief Executive David Gallop said in a statement on Thursday.
"It's just a longer, harder road but we are focused on supporting Ange, his support staff and the playing group.
"We are experienced in the challenges of being on the road for away games but being at home brings our players in from the four corners of the globe and we expect it to be a big occasion for the football family and the nation."
The first leg of the final round of Asian qualifying will be played on Oct.5, with the second leg in Sydney on Oct. 10.
Syria have been playing their "home" World Cup qualifiers in Malaysia because of the security situation in the war-torn country.
The winner then faces the fourth-placed side from the North and Central America CONCACAF region, which is currently the United States with two matches remaining, in a two-legged playoff in November.
Australia have featured in the last three editions of the World Cup finals.
(Reporting by Greg Stutchbury; Editing by Nick Mulvenney)
