Leeds crashed to their second UEFA Cup defeat of the season - but a 'Battle of Britain' semi-final showdown with Arsenal is still on the cards.

Boss David O'Leary's young guns and Arsene Wenger's Gunners are seemingly on a collision course after their victories on Thursday.

It will surely come as no surprise if Leeds find themselves up against their bitter Premier League rivals on Friday when the draw is made in Geneva.

O'Leary has already admitted he fears facing his former club over two legs as he feels they will go on to win the tournament given their experience and pedigree.

The 41-year-old Irishman would prefer to meet Arsenal in the final in Copenhagen - but the suggestion is UEFA are unlikely to keep the two teams apart.

It would mean Leeds facing yet another Champions League side on what has so far been an unforgettable European journey, with the Czech League leaders now their latest conquests, despite a shock defeat.

With United seemingly with one foot in the semi-finals after last Thursday's 3-0 first-leg victory at Elland Road, they then achieved their primary target of keeping Slavia at bay in the first half - and it proved crucial.

It then took Leeds just a minute of the second half to prise open the Slavia defence and score the vital away goal which led to a mountainous task taking on Everest-like proportions for the home side.

Leeds had created several incisive openings during the first 45 minutes, but this was a sweet move as Slavia had no answer to United's cut and thrust.

Eirik Bakke was the instigator with a short pass to Stephen McPhail, but it was the young Irishman's piercing through-ball which sliced open the home defence.

Harry Kewell timed his run to perfection as he beat the offside trap before a first-time left-foot shot from 15 yards beyond keeper Radek Cerny.

The jewel in Leeds' crown had again sparkled, scoring his 15th goal of the season - his fifth in Europe - and his fifth in successive games.

The Australian international is now proving a lethal weapon up front, with O'Leary spot-on in his judgement that Kewell was made for the role.

The 21-year-old has relished playing as a striker after being switched from his previous left-wing role earlier this year, and there now seems no stopping him - nor his soaring transfer value.

It soon proved to be one of his most vital goals of the season as Slavia then hit back just six minutes later when Ivo Ulich scored what appeared to be at that stage a mere consolation.

But when Ulich rattled home a spot-kick 11 minutes from time after Ian Harte had brought down Ludek Zelenka, the importance of Kewell's 46th-minute opener became even more apparent.

It had earlier been a case of Leeds being patient, just like a week ago when they eventually made the breakthrough just before half time and then going on to comprehensively dismantle Slavia.

Goals from Jason Wilcox, Kewell and Lee Bowyer, on what was another glorious European night at Elland Road, had provided a seemingly insurmountable cushion.

Coach Frantisek Cipro had admitted his players had been "frightened" by the intimidating atmosphere in Yorkshire, and ran off the ball by the pace of United's energetic side.

Realising such cut-and-thrust exuberance had undermined the Czechs on that occasion, O'Leary went for the youngest midfield line-up he has had the opportunity to employ.

Eirik Bakke, Stephen McPhail and Matthew Jones - aged just 21, 20 and 19 respectively - provided the beating heart of an attacking 3-5-2 formation.

With O'Leary again opting for three at the back, which had kept Italian giants Roma at bay in the grandeur of the Stadio Olimpico in the last round, it meant a return to the side for Jonathan Woodgate.

To add to Cipro's problems, he was without skipper Karel Rada following his dismissal for two bookable offences last week, although star striker Zelenka returned after serving his one-match ban.

Without the steadying hand of Rada, Leeds were certainly the more dangerous in the first half as they created several clear openings, only for Cerny to keep his side in the game with two superb saves from McPhail and one from a Harte free-kick special.

Although Kewell also missed a sitter when all alone at the far post from a Bridges cross, it was a momentary indiscretion he can easily be forgiven for given the worth of his strike tonight.

Slavia threatened towards the end of the half, with towering captain colossus Lucas Radebe throwing himself in front of a Zelenka shot when presented with a clear sight of goal after he had turned inside Alfie Haaland.

Then, after Ulich had first cancelled out Kewell's opener, the home side visibly grew in confidence despite their task having been made more difficult by the away goal.

Although Ulich completed his brace from the spot to condemn Leeds to their first defeat in seven games, and ending a five-match winning streak, United had thankfully already done enough in a decisive first leg to seal their semi-final place.

Teams:

Slavia Prague: P. Cerny, Kozek, L. Dosek, Koller, Hysky, Ulich, Dostalek (Lerch 53), Skala, Kuchar (Vozabal 85),T. Dosek (Vagner 53), Zelenka.

Subs Not Used: Kristofik, Vaclavik.

Booked: Koller, Lerch. Goals: Ulich 52, 79 pen.

Leeds: Martyn, Woodgate, Haaland, Radebe, Kelly, Bakke, Jones, McPhail, Harte, Bridges (Smith 50), Kewell.

Subs Not Used: Robinson, Hopkin, Huckerby, Mills, Duberry,Wilcox.

Goals: Kewell 47.

Agg (2-4)

Att: 13,460

Ref: Sarvan Ozun (Turkey).