Iran will play hosts and holders Qatar or Uzbekistan in the Asian Cup semi-finals after Alireza Jahanbakhsh scored a 96th-minute penalty for a dramatic 2-1 win over Japan on Saturday.

It was a stunning comeback from Iran, who were behind at the break but roared back to dump out the pre-tournament favourites and keep alive their dream of a first Asian title since 1976.

Hidemasa Morita gave Japan, who were looking to lift the trophy for a record-extending fifth time, the lead midway through the first half in front of 36,000 at Education City Stadium.

Mohammad Mohebi drew Iran -- themselves champions three times -- level 10 minutes after half time and they dominated the remainder of the game.

But just when it looked like extra time, Kou Itakura brought Hossein Kanaanizadegan down in the box deep in stoppage time and Jahanbakhsh held his nerve from the spot.

Iran, missing the suspended Porto forward Mehdi Taremi, had the first sight of goal on 13 minutes when Feyenoord winger Jahanbakhsh fizzed the ball just over goalkeeper Zion Suzuki's crossbar.

Japan seemed flustered initially by their opponents' physical approach, but they were able to give as good as they got and Itakura picked up a yellow card for cynically stopping an Iran attack.

On 28 minutes Hajime Moriyasu's side went ahead when Morita bustled his way through a weak challenge and with Iran's defence AWOL, the midfielder was all alone with only Alireza Beiranvand to beat.

He did not strike the ball convincingly but the goalkeeper tried to save with his legs instead of his hands and the ball hit an outstretched limb before looping into the net.

Six minutes before the break Iran, who squeezed through on penalties over Syria in the last 16, might have drawn level but Saman Ghoddos pulled his snapshot wide.

Japan, beaten by Qatar in the 2019 final, went to the break in the lead but there was little in it.

In the 55th minute Iran pulled level when Sardar Azmoun slipped in Mohebi and he beat an exposed Suzuki with a clinical first-time finish.

It was all Iran now. Mohebi headed just wide at the far post and then an Azmoun header flashed narrowly past Suzuki's post with the goalkeeper beaten, before the late drama at the death.

Qatar face Uzbekistan later Saturday with South Korea playing Jordan in the first semi-final, on Tuesday.