Leeds reached an FA Cup semifinal for the first time in 39 years -- but only via a penalty shootout after they blew a two-goal lead in stoppage time.

Thousands of West Ham fans left early as the clock ticked round to 90 minutes after goals from Ao Tanaka and Dominic Calvert-Lewin put Leeds 2-0 up.

But those who left prematurely missed a cast-iron cup classic, starting with an astonishing comeback as goals from Mateus Fernandes and Axel Disasi forced a 2-2 draw and extra time.

They also missed 20-year-old fourth-choice goalkeeper Finlay Herrick thrown on for his debut in the shootout after Alphonse Areola went down injured at the death.

Herrick saved the first spot-kick from Joël Piroe, but Leeds keeper Lucas Perri denied Jarrod Bowen and Pablo Felipe to send Leeds through 4-2 on penalties.

There was controversy after Leeds were told the shootout could not be taken in front of their fans due to "safety concerns."

But the visitors shrugged that off to book a trip to Wembley for a first FA Cup semifinal since 1987.

With both these teams knee deep in the Premier League relegation scrap, there were suggestions this match was an unwanted distraction. Not so, as it turned out.

A frenetic encounter began when Leeds deservedly went ahead in the 26th minute, Noah Okafor and James Justin combining to set up Tanaka.

The Japan international showed quick feet in a crowded penalty area, turning Soungoutou Magassa before drilling in a low shot which flicked off Hammers defender Disasi and looped in over Areola.

Six minutes later West Ham had a lucky escape after Leeds broke forward and Okafor played in Anton Stach, whose shot was saved by Areola.

Stach was on the end of a clumsy, late challenge from Max Kilman after he had got his shot away.

VAR took a long look at the tackle but decided not to award a penalty, even though Stach was unable to continue.

West Ham pushed in the second half and Taty Castellanos met Adama Traoré's cross with a diving header which struck the far post.

They had Leeds penned in -- but then Kilman stepped in again. The £40million ($53m) centre-half launched into another ill-advised tackle in the area, this time on Brenden Aaronson.

The ball was there to be won, but somehow Kilman still managed to miss it completely and take the Leeds substitute out.

This time referee Craig Pawson was sent to the screen before awarding the penalty and booking Kilman before Calvert-Lewin confidently converted the spot-kick.

But West Ham pulled one back in stoppage time when Fernandes converted the rebound after Bowen's shot came back off the far post.

Then Disasi prodded in Traoré's cross to drag the Hammers level, despite Leeds' protests that his high boot caught Pascal Struijk.

The thousands of West Ham fans who had left early were trying, and failing, to get back in when Castellanos thought he had put them ahead in the opening seconds of extra time after a bad error from Perri, only for VAR to rule him offside.

Then Bowen crashed a shot again the crossbar, with Pablo offside when he rolled in the rebound.

Areola went down injured with five minutes of extra time remaining, leaving Herrick to take centre stage, but it was Perri who proved to be the hero as Leeds landed their date with Chelsea at Wembley.