Leeds boss David O'Leary will have to wait until next Tuesday if he is to celebrate his 43rd birthday with the present of a place in the Champions League final he so desperately craves.

O'Leary had been hoping to look back on today as the birthday of a lifetime, but it was not to be as Valencia gained a vital stranglehold on this semi-final by holding the Irishman's braves to a goalless draw.

Leeds now face an uphill task if they are to qualify for a showdown with either Real Madrid or Bayern Munich, with their only saving grace the fact they managed to keep what could prove to be a priceless clean sheet at Elland Road.

Leeds' record in Spain, however, is a miserable one as O'Leary's young lions have lost all three matches they have played against La Liga giants Real, Barcelona and Deportivo La Coruna this season by a combined aggregate of 9-2.

The mauling Leeds sustained at the hands of Deportivo three weeks ago will still be fresh in the minds of players who, according to O'Leary, froze on a night of high drama at the Riazor Stadium.

In defending a 3-0 lead, Leeds held on by the skin of their teeth, losing 2-0 in La Coruna but taking their last four place against Valencia 3-2 on aggregate.

O'Leary will need to ensure his side do not act like scared rabbits again if they are to grace the final at the San Siro in Milan on May 23 with this tie resting on a knife edge.

But they head into the cauldron of the Mestalla next Tuesday knowing Valencia have not been beaten at their European fortress in the Champions League during the past two seasons.

This first leg was certainly the battle Leeds had been expecting, but not quite the "war" Valencia had prepared themselves for, despite clear signs of needle from both sides during a tie with a number of flashpoints.

Leeds had been described as 'thugs' by the Spanish media and one moment of madness by Lee Bowyer a third of the way into the game lent a touch of credence to the claims.

Valencia coach Hector Cuper had ordered his players to practice kicks, elbows and shirt pulls in preparation for this tie, fully expecting Leeds to play dirty.

What appeared to be a stamp from Bowyer, United's leading scorer in the Champions League this season, on Juan Sanchez was missed by hardline Italian referee Pierluigi Collina.

Sanchez understandably refused Bowyer's hand of friendship, with the 24-year-old midfielder then receiving a verbal volley from Amedeo Carboni and having to be pulled away from a potentially heated situation by Rio Ferdinand.

But despite exactly half the players on the pitch - four Leeds and seven Valencia - one booking away from suspension and automatic ban for the second leg at the Mestalla next Tuesday, the yellow card remained firmly in Collina's pocket.

Instead, the first half was an even affair as both sides had the chances to break the deadlock, with Leeds starting like a bullet out of a gun.

They should have drawn first blood, with Alan Smith - singled out before the game by Roberto Ayala as the man to stop at all costs - quickly incurring the first foul.

Mauricio Pellegrino bundled over the 20-year-old in the fourth minute, setting up Ian Harte for a trademark free-kick, with the left-back curling in a 20-yard stunner which Santiago Canizares only just tipped over the bar.

From the resultant Harte corner, Matteo flicked the ball on for an awaiting Harry Kewell at the far post, but the Australian international made a hash of his attempted volley, horribly miscuing.

With Leeds enjoying the early pressure, David Batty then struck a superb right-foot drive from 25 yards, one which stung the fingers of Canizares as the Valencia keeper held on to the ball at the second attempt.

After weathering the early storm, Nigel Martyn twice had to be at his brilliant best to deny last season's beaten finalists who were able to carve out clear chances.

Juan Sanchez was the instigator of the first in the 12th minute, whipping in a right wing cross which was met in spectacular fashion by John Carew as the Norwegian international connected with an overhead volley from 12 yards.

Martyn superbly pushed the ball away to his left, and again showed great agility in the 41st minute after a mistake from Ferdinand, as an attempted clearing header fell straight into the path of the awaiting Sanchez for a first-time half-volley which the 34-year-old keeper tipped beyond the post.

In between, though, it was a Martyn mistake which gifted Valencia their best chance of the match as a poor punched clearance from a Kily Gonzalez cross led to influential skipper Gaizka Mendieta looping a header onto the bar.

Six minutes from the break, another Harte free-kick was almost the undoing of Valencia, this time the Republic of Ireland star picking out Kewell at the far post with a deep inswinger.

Kewell knocked the ball back across the six-yard box, with Rio Ferdinand missing the first opportunity, albeit helping the ball onto the far post where Smith headed wide, ultimately taking the chance off Mark Viduka who had been staring at an open goal.

After missing such a glaring opportunity, if Leeds felt this was not going to be their night then worse was to follow in the seven minutes after the break.

Harte was again the instigator with a corner flicked on by Bowyer, with the ball flashing through the six-yard box for an all-alone Dominic Matteo waiting at the far post.

It seemed all Matteo had to do was steer the ball goalwards for the opener, but despite a firm header from no more than four yards out from the centre back, somehow Canizares managed to scramble back across his line to palm the ball away.

Valencia's defence - having conceded just nine goals in their 14 previous Champions League matches - underlined just why they are so hard to break down as they held firm under incessant Leeds pressure, but with chances at a premium.

Instead it was Valencia who almost stole the show and nearly ruined O'Leary's day altogether with Vicente - a 90th minute sub for Kily Gonzalez - powering in a header which bounced over Martyn, only for Ferdinand to produce a critical clearance off the line.

The stage is now set for heroics in the return and Leeds may only need an away goal - the tie is far from over.

Teams:

Leeds: Martyn, Mills, Harte, Ferdinand, Matteo, Bowyer, Dacourt, Batty, Kewell, Viduka, Smith.

Subs Not Used: Robinson, Kelly, Woodgate, McPhail, Wilcox, Bakke, Burns.

Valencia: Canizares, Angloma, Pellegrino, Ayala, Carboni, Albelda, Baraja, Mendieta, Kily Gonzalez (Vicente 90), Sanchez (Zahovic 67), Carew.

Subs Not Used: Palop, Deschamps, Djukic, Aimar, Aurelio.

Booked: Baraja, Carboni.

Att: 36,437

Ref: Pierluigi Collina (Lucca).