The shoot-out became the circuit-breaker after both teams had played themselves to a standstill over the regulation 90 minutes and 30 minutes' extra time without scoring a goal.

The Koreans held their nerve with their veteran goalkeeper Lee Woon-jae proving the hero when he saved efforts from Mehdi Mahdavikia and Rasoul Khatibi to acclaim from the chanting Korean supporters.

It was the second quarterfinal at the tournament to go to a shoot-out after Japan knocked out Australia 4-3 on penalties in Hanoi on Saturday.

"Clearly I am very, very proud of the boys. It was very hard against strong opposition," said Korea's Dutch coach Pim Verbeek, who singled out their spirit for praise.

"Mentally we were very strong. I've never seen a Korea team not play with spirit, that's why it is a pleasure for me to work with them."

While ecstatic, Verbeek knows plenty of hard work remains with just two days to recover from the energy-sapping match before facing Iraq here on Wednesday.

"We have nothing with a semi-final, we must go for the final," he said.

It was huge relief for South Korea, who had been beaten twice in their three previous quarterfinals with Iran at the Asian Cup.

South Korea twice won the Asian Cup in the origins of the tournament in 1960 and 1964 and despite finals appearances in 1972, 1980 and 1988 have yet to add another trophy.

They are now just one game away from the July 29 final in Jakarta.

It was tough uncompromising football with solid challenges and a large number of fouls with the Koreans giving as good as they got from three-time champions Iran, a pre-tournament favourite.

Midfielder Mehrzad Madanchi became the first player booked when he brought down livewire Korean striker Lee Chun-soo midway through the opening half.

South Korea almost caught Iran on the counter with slick passing for Lee to race clear but he was deemed to have fouled Madanchi and the chance was wasted.

Woon-jae was forced to make an important body block on Ali Karimi's close-range volley a few minutes from half-time, and defender Kim Jin-kyu needed to make a hurried clearance to keep his team's goal intact right on the berak.

Striker Yeom Ki-hun almost broke the deadlock on the hour when his shot bobbled off the wet surface and Rodbarian did well to turn it away for a corner and keep his goal intact.

The match went into extra-time and Javad Nekounam looked poised to score at the end of the first period when his drive off a Karimi lay-off flashed just wide of the left post.

In the final minute of extra-time Iran coach Amir Ghalenoei switched goalkeepers with Vahid Talebloo coming on for Rodbarian as he planned his strategy for the penalty shoot-out.

Ghalenoei defended his controversial tactic.

"He is very good with penalties, he saved 17 in training so I beleived in that substitution," he said, adding that he would review his position once the dust has settled as he prepares for a backlash in Tehran.

"We did well tactically and physically," he said. "I insist on taking full responsibility for the result. The Iranian players need to be supported for the future."