Japan won a tense penalty shootout here after a gruelling 120 minutes of football ended with the scores locked at 1-1 to set up a last four showdown with either Saudi Arabia or Uzbekistan who play on Sunday.

Iraq was a class above Vietnam in Bangkok, running out comfortable 2-0 winners to set up a semi-final clash with arch rivals Iran or 2002 World Cup semi-finalists South Korea.

Goalkeeper Yoshikatsu Kawaguchi was Japan's hero, blocking the Socceroos first two spot kicks from Harry Kewell and Lucas Neill, with Yuji Nakazawa scoring the decisive penalty.

Two goals in the space of three minutes in the second half sparked the game into life, with John Aloisi making the breakthrough for Australia in the 69th minute only for Naohiro Takahara to level soon after.

"The Japanese team achieved a lot tonight," said elated coach Ivica Osim, who retreated to the locker room after extra time and did not watch the penalties.

"I thought that if I watched Japan might lose," he explained.

"I didn't see the television in the dressing room so I didn't know the progress but when I heard the news I jumped and hit the ceiling."

Australia was reduced to 10 men with 15 minutes to play after Vince Grella was sent off for elbowing Naohiro Takahara but a tired Japan failed to capitalise as the game went to extra-time in hot and humid conditions.

Both coaches had been keen to play down the revenge aspect of the game following Australia's 3-1 victory over Japan at the World Cup in Germany, but it was clear the Blue Samurai desperately wanted to win this one.

Australian coach Graham Arnold, who faces an uncertain future, said he was proud of his team despite the loss.

"I'm extremely proud of the way my players performed in those conditions, a man short. They worked very hard," he said.

"We have learned a lot these past couple of weeks. Asia is very difficult.

In Bangkok, Younis Mahmoud scored a brace to ensure the war-ravaged nation has something to cheer about, although Vietnam, who few expected to make it this far, did themselves proud.

Mahmoud did the damage with a strike in the second minute and the plukcy Vietnamese never fully recovered, with the Al Gharafa forward putting it beyond their reach in the 66th minute with a beautifully struck free-kick.

The victory was a ray of light for the beleaguered Iraqi people who have previously celebrated their team's victories with rounds of gunfire into the night sky.

It is only the second time that Iraq have made the last four, having been thwarted at the quarter-final stage at the last three Asian Cups.

The Iraqis stumbled to United Arab Emirates in 1996, Japan in 2000, and China in 2004, but they were always in charge against Vietnam, playing in their first Asian Cup for 47 years.

Vietnam's Austrian coach Alfred Riedl before the game called on his youthful team to play like men and not boys, but they were physically out-matched by the bigger Iraqi players who were superior in the air.

The double took Mahmoud's goal tally to three for the tournament, one behind Japan's leading sharpshooter Takahara.