Iran and Brazil, along with host Russia, are the only teams so far assured of a place at the 2018 World Cup. Three more Asian teams will secure their place in the tournament draw in December over the next week as qualifying resumes.
With Iran already securing qualification from Group A, South Korea and Uzbekistan are vying for the second automatic qualifying spot. In Group B, there is a three-way tussle between Japan, Saudi Arabia and Asian Cup champion Australia to finish in the top two.
The two third-place teams from each group will contest a playoff in October to determine who goes into an intercontinental qualifier against the fourth-place team in qualifying from CONCACAF, the North and Central America and the Caribbean confederation.
After all the upheaval from two recent losses that cost Uli Stielike his job as coach, South Korea has a one-point cushion over third-place Uzbekistan and can secure a place in Russia with victory at home against unbeaten Iran on Thursday - if Uzbekistan loses in China. Any other combination of results will leave the second spot up for grabs when the South Koreans travel to Tashkent five days later for its final group game.
South Korea has qualified for the last eight World Cups, and former South Korea midfielder Shin Tae-yong has taken over as coach with the sole aim of extending that streak to nine.
Fourth-place Syria, which is four points behind South Korea and still has a chance to qualify automatically, will play Qatar on neutral territory in Malaysia on Thursday. China and 2022 World Cup host Qatar each need two wins from the last two matches to stay in the mix.
Second-place Saudi Arabia kicks off match day nine at the fourth-place United Arab Emirates in a strong position to return to the World Cup for the first time since 2006.
Japan leads the group with 17 points, a one-point buffer over Australia and Saudi Arabia - countries it will meet in its last two games in Saitama and Jeddah, five days apart - and seven points clear of the UAE.
The Japanese could secure qualification for a sixth consecutive World Cup with a win over Australia, but two losses or two draws over the six-day span could see them slip to third.
Unbeaten Australia will be without injured captain Mile Jedinak. Tim Cahill, a veteran of three World Cups and 100 games for Australia, is hoping his team can finally produce its first win in Japan since 1969.
''I'm very focused on being prepared and making sure we are ready for such a big occasion,'' Cahill said.
Thailand hosts Iraq on Thursday in a game between two teams which have no chance of making it to Russia.
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