With the event in Thailand offering three places at the Games, the winners of the last-four matches knew they would be guaranteed a spot in Japan.

The South Koreans will play at an eighth consecutive Olympics after beating Australia 2-0 in Rangsit.

Saudi Arabia will play at their second Games, and their first since Atlanta 1996, after winning 1-0 in Bangkok against defending champions Uzbekistan.

Both winners will contest Sunday's (January 26) final in Bangkok, while Australia will take on Uzbekistan in the third-place match on Saturday (January 25), when the last Tokyo 2020 spot will be on the line.

The Koreans were dominant at Thammasat Stadium and took a deserved lead on 56 minutes, when Kim Dae-won scored on the rebound after Lee You-hyeon had struck the bar.

Lee Dong-gyeong added a second which went in off the post on 76 minutes to make the game safe.

South Korea, who won Olympic bronze at London 2012 after knocking out hosts Britain on penalties in the quarter-finals, have never won the Asian under-23 title.

Their best finish was runners-up to Qatar at the second edition in 2016.

Saudi Arabia have also never won the event, which means new champions will be crowned.

They lost the inaugural final in 2013 to Iraq and left it late to end Uzbekistan's title defence amid high drama at Rajamangala Stadium.

Nasser Al Omran fired in an effort with three minutes to play, which was deflected home by Abdullah Al Hamdan to settle the contest.

Uzbekistan were hoping to book their first Olympic appearance but must now get by Australia, who have made the Games five times.