Two goals in eight minutes either side of the break kept the Tangerine Scottish Cup dream alive as Dundee United advanced to a semi-final confrontation with Celtic on April 10.

It was harsh luck on First Division Ayr, who had been marginally the better side during the opening period, pulled back from conceding a disastrous first-half goal but succumbed to a header from Swedish defender Magnus Skoldmark.

The game seemed to be meandering towards the interval when Ayr keeper David Castilla committed suicide, racing to the edge of his area to punch clear a harmless Joe Miller cross.

Castilla could only punch straight to Neil Murray, who volleyed a first-time shot back into the empty net from 30 yards.

Ayr responded a minute after the break when Andy Walker bundled home a Gary Teale corner but Skoldmark, whose solidity and aerial power epitomise this Dundee United side, flicked home from eight yards.

Having already played enough matches to win the competition, the home side went into their third successive replay without Jim Paterson (cracked vertebrae) and suspended pair Jason de Vos and Darren Paterson.

In contrast, Ayr boss Gordon Dalziel was able to pick from full strength, with Andy Walker, who missed the late penalty which would have won the first game, again partnering Glyn Hurst up front in an unchanged line-up.

Ayr enjoyed the best of the opening period, passing the ball around rather than follow the home side's preference for the aerial route.

Gary Teale found acres of space down the Ayr right but delayed on too many occasions, denying his side the opportunity of creating a decent chance.

The Premier League side had more joy in the air and could have scored as early as the second minute but John Eustace headed tamely at Castilla from close range.

Eustace thought he had scored when a John Traynor clearance rebounded off him and into the net.

But referee Stuart Dougal's only award was a yellow card for deliberate handball as Eustace charged the ball down.

Sieb Dijkstra needed to be at full stretch to tip Teale's free kick round a post as the first half drew to its final frenetic close.

And the United keeper was called on again after Murray had put the home side in front, a fingertip touching Millen's shot onto the crossbar.

The rapid-fire start to the second period only increased the intensity as Ayr pushed further forward in a desperate bid to grab an equaliser.

But the First Division side left gaps at the back and Kjell Olofsson wasted a glorious chance to seal the win when he headed wide from close range when it looked easier to score.

Gordon Dalziel's men lacked nothing in heart and fight but though their play was more pleasing to the eye, it lacked the guile needed to open up their illustrious opponents.

Teams

Dundee Utd: Dykstra, Skoldmark, Malpas, Murray, Duffy, Jonsson, Miller (McLaren 87), Eustace, Olofsson, Dodds, Easton.

Subs Not Used: Mathie, McNally.

Booked: Eustace.

Goals: Murray 42, Skoldmark 51.

Ayr: Castilla, Robertson, Barrick, Millen, Traynor (Reynolds 78), Craig, Hurst, Davies, Walker, Teale, Lyons (Ferguson 72).

Subs Not Used: Nelson.

Booked: Traynor, Hurst.

Goals: Walker 46.

Att: 7,313

Ref: S Dougal (Glasgow).