Syrian football fans have trolled Australia's official Facebook supporters page ahead of Tuesday's World Cup play-off in Sydney, flooding it with thousands of messages.

Asian champions Australia are favourites to win the play-off after a late penalty earned Syria a controversial 1-1 draw in the first leg in Malaysia last week.

The match has galvanised fans of the Qasioun Eagles, with thousands posting on the Socceroos page in Arabic and English.

"We will beat you in Sydney and then we will have sometime to eat kangaroo barbecue before we go back SYRIA," one commentator wrote, while another added: "Are you walking in Australia or jumping like kangaroos?"

Syria's success in World Cup qualifying has come despite an ongoing civil war, and some fans wrote emotional posts about the significance of a win over Australia.

"After 7 years I think this page is the only place brings all the syrians together," one poster wrote.

"BTW we are just here for kidding .. With our respect for your national team and country. But #Never_stop_Dreaming."

Another added: "Syria needs to qualify more than Australia because the Syrian people are sad and in need of joy. We need something from our country."

Some Australian users called on the Syrians to comment on their own supporters' page, while others wished both teams the best for the game at ANZ Stadium.

Australia, ranked 50th, have played the last three World Cups, reaching the last 16 in 2006.

Syria, ranked 75th, have never reached the World Cup before. They needed an injury-time equaliser against Iran last month to take them into the Asian play-off.

The winner of the play-off will face the fourth-placed CONCACAF federation team, currently Panama, over two legs for a place at Russia 2018.

The 17 nations that have already booked their place for the 2018 World Cup in Russia following Monday's qualification of Iceland and Serbia:

Europe: Belgium, England, Germany, Iceland, Poland, Russia (as hosts), Serbia, Spain

Africa: Egypt, Nigeria

Asia: Iran, Japan, Saudi Arabia, South Korea

North, Latin America: Costa Rica, Mexico

South America: Brazil