The Iranian team, headed by Aleksandar Ciric, defeated South Korea 17-8 on Wednesday in Pool A.
Iran will play Kazakhstan on Thursday in the most important match of the qualifying round.
Earlier, Iran defeated India 19-4 at the Championship opening match on Tuesday.
Group B consists of Japan, China, Singapore, Hong Kong, and Kuwait.
The competition is being held in Bang Sao Thong district, Samut Prakan province, Thailand from Nov. 7 to 13.
The Asian Water Polo Championship serves as a qualification for the 2023 World Water Polo Championship to be held in Fukuoka, Japan.
The top two teams as well as hosts Japan will take part in the world championship.
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