Australia's hopes of automatic qualification for the 2022 World Cup in Qatar were rocked by a late Abdullah Fawaz penalty as Oman claimed a 2-2 draw with Graham Arnold's side in Muscat on Tuesday.
Jamie Maclaren's 15th-minute penalty put Australia ahead but Fawaz levelled with a drive into the top corner in the 54th minute.
Aaron Mooy restored Australia's lead 11 minutes from time when he shot past Faiyz Al Rashidi, only for Fawaz to score from the spot following Fran Karacic's foul on Muhsen Al Ghassani.
Australia remain third in Group B of the Asian qualifiers but are now four points behind Saudi Arabia and three adrift of Japan, with games against the leading pair to come in the final two rounds of games in March.
Japan closed in on the finals with a 2-0 victory over the Saudis at Saitama Stadium.
Takumi Minamino and Junya Ito were on target for the Samurai Blue as they handed Herve Renard's side a first defeat of the current round of preliminaries.
Winger Ito rolled the ball to Minamino and his powerful attempt beat Mohammed Al Owais in the 32nd minute.
Five minutes after the restart, Ito went from provider to goalscorer with a stunning strike from the edge of the area, leaving Al Owais with no chance as the ball flew into the top corner.
Vietnam picked up their first win of the campaign as their 3-1 victory in Hanoi ended China's slim hopes of finishing third in the group.
South Korea booked their place in Qatar after Paulo Bento's side beat Syria 2-0 in Dubai to confirm their progress to a 10th consecutive finals.
Second-half goals from Kim Jin-su and Kwon Chang-hoon ensured the Koreans continue a run of successive qualifications that stretches back to Mexico in 1986 as they wrapped up a top-two finish in Group A.
Kim put the Koreans in front eight minutes into the second half, with the Jeonbuk Motors left-back rising to meet Kim Tae-hwan's cross from the right as he powered his header home.
Kwon made sure of the win 18 minutes from full-time with a dipping left-footed strike from outside the area that bounced beyond goalkeeper Ibrahim Alma.
Only the top two finishers in each of Asia's two qualifying groups can claim guaranteed berths at the finals, while the third-placed nations will face off for the right to meet South American opposition in an intercontinental playoff.
Iran, who claimed their ticket for for the finals with a 1-0 win over Iraq on Thursday, defeated the United Arab Emirates 1-0 through a Mehdi Taremi goal to remain on top of Group A.
Lebanon remain fourth in the group after recording a 1-1 draw against Iraq in Sidon.