KUALA LUMPUR (REUTERS) - Asian football champions Australia were grouped in a formidable pool alongside Saudi Arabia, Japan and the United Arab Emirates in the third round of 2018 World Cup qualifying on Tuesday.

Joining the quartet in Group B were 2007 Asian champions Iraq and a fast-improving Thailand.

Group A was headlined by consistent qualifiers South Korea and Asia's top-ranked team Iran, who both represented the continent at the last World Cup in Brazil along with Australia and Japan.

China, Qatar, Syria and Uzbekistan were also drawn in Group A.

The top two from each pool will qualify for Russia 2018, with the two third-placed sides facing off to see who will advance to a two-legged inter-confederation play-off with a North and Central American qualifier, for another spot in Russia.

The round-robin matches will start on Sept 1.