Tim Cahill capped the biggest week of his career to date with a precious goal to fire First Division Millwall to an FA Cup final clash with Manchester United - and into Europe.

The Australian saw his nine-year battle to represent his country finally come to fruition in midweek, and claimed the only goal of the game on 25 minutes to condemn Nationwide League counterparts Sunderland to a heart-breaking defeat at Old Trafford and book his club their first ever trip to the showcase final.

Cahill shot past Mart Poom after the Estonian had saved Paul Ifill's shot following an error by Black Cats' skipper George McCartney to ensure that Dennis Wise's men completed a treble over the Wearsiders this season and ended hopes of a repeat of their FA Cup heroics in 1973.

The victory was down to a combination of hard work, a little more composure and a cool head when it mattered, although had it not been for Poom's brilliance, former Sunderland striker Danny Dichio would have wrapped it up with a second goal 16 minutes from time.

McCartney almost redeemed himself at the death, but saw his 86th-minute shot curl agonisingly wide, and his side's misery was completed when Jason McAteer picked up a second yellow card and was sent off.

For both clubs, the main focus this season has been - and remains - promotion to the Barclaycard Premiership - but for 90 minutes this afternoon that was put on hold as they chased the most unlikely of prizes.

Not only a dream trip to Cardiff and a date with Premier League aristocrats Manchester United awaited the winners, but also a place in next season's UEFA Cup, something which was beyond the wildest dreams of even the most optimistic of supporters of either persuasion just a few months ago.

Simply reaching this stage of the competition was remarkable enough, particularly for the Wearsiders, who plunged out of the top flight with massive debts at the end of the last campaign, while Millwall's resurgence under player-coach Wise was a story in itself.

For Wise's men, a double of sorts is still on; for Mick McCarthy's side, the business of returning to the top flight is now the only concern, resuming at Wimbledon on Tuesday night.

If the Londoners settled the better with Wise exercising a measure of control from the middle of the field, it was the Black Cats who created the more promising openings in the early stages.

Indeed, they came agonisingly close to taking a seventh-minute lead when, after Cahill had been penalised for a trip on McAteer 25 yards out, John Oster curled a free-kick over the defensive wall and, with keeper Andy Marshall beaten, against the crossbar.

The Welshman fired another shot just over two minutes later after linking well with Julio Arca, although as the first half wore on, it became a concern for McCarthy that his side were not getting the Argentinian, perhaps their most creative player, into the game often enough.

Oster turned up inside his own penalty area with 17 minutes gone to hack away a Neil Harris cross after the hard-working striker had forced his way in down the right, and the Lions had their tails up.

However, they needed a helping hand to take the lead, and it came from unfortunate McCartney eight minutes later.

The Northern Ireland international left his lay-off to Phil Babb woefully short to allow the lively Ifill to steal in and head for goal.

And although Poom managed to beat his well-struck shot away, Cahill was on hand to hook home the rebound and spark delirious celebrations.

Ifill's afternoon was to end prematurely when he was stretchered off four minutes later, soon to be followed by tough-tackling defender Kevin Muscat, courtesy of McCartney's agricultural challenge, although he had earlier been involved in an untidy spat with McAteer which sparked something of a melee.

Wise, who had once again stamped his authority on the game, saw a free-kick deflected wide eight minutes before the break, but the Wearsiders rallied as the whistle approached.

Arca fired into the side-netting from a tight angle in injury time, but there was a growing suspicion that no-one wanted to take the responsibility for McCarthy's men as a series of shooting opportunities were passed up.

Kevin Kyle, however, remedied that situation in a blistering start to the second half, first hammering a right foot shot wide after his initial effort from a Steven Wright cross had been blocked and then testing Marshall with a downward header.

Sunderland's cause might have been lost 16 minutes from time, though, when Cahill broke down the right and crossed for Dichio, whose header was saved at point-blank range by Poom. Still there was hope.

McCarthy threw caution to the win as the game entered its death throes, replacing defender Babb with winger Matt Piper, and McCartney had a glorious opportunity level six minutes from time, but curled his effort inches wide.

Sunderland's day took a turn for the worse two minutes later when McAteer was dismissed for his second bookable offence.

A late Piper effort was turned away by Marshall, and the final whistle brought Sunderland's FA Cup dream to an end as Wise's Millwall marched on to more adventures.

Teams

Sunderland Poom, McCartney, Babb (Piper 77), Breen, Wright (Thornton 90), Arca, Thirlwell, McAteer, Oster, Kyle (Stewart 61), Tommy Smith.

Subs Not Used: Williams, Myhre.

Sent Off: McAteer (86).

Booked: McAteer, McCartney, Thirlwell.

Millwall Marshall, Lawrence, Muscat (Roberts 42), Ward, Livermore, Cahill, Wise, Ifill (Sweeney 29), Dichio, Ryan (Elliott 56), Harris.

Subs Not Used: Gueret, Chadwick.

Booked: Ifill, Wise.

Goals: Cahill 26.

Att: 56,112

Ref: P Durkin (Dorset).