Both teams were also looking to get the decisive breakthrough as soon as possible with Messi involved in almost every Barca raid. However it was defender Eric Abidal who had the first goal attempt when his lofted 25-metre shot just went over the United bar.
MISPLACED PASS
United though did strike the decisive goal when Cristiano Ronaldo attempted to run at the Barca defence but lost the ball to Gianluca Zambrotta whose misplaced pass found Scholes.
He controlled it, let it bounce and then swerved it past Valdes from 25 yards. It was his 21st goal in his 101st Champions League appearance but only his second goal in any competition this season. Few could have felt better.
United had two good chances to increase their lead in the opening half through Park Ji-sung, who sidefooted wide after 21 minutes and then when Nani headed a Park cross wide after 41 minutes.
Barcelona's best chance inevitably came from Messi who weaved his way past Scholes and Brown after 20 minutes and forced Edwin van der Sar into a diving clearance before Deco had two good chances to score in three minutes sending his first over the bar and his second narrowly wide.
A chill descended on Old Trafford when Barca brought on Thierry Henry for Andres Iniesta after an hour and United's old Arsenal nemesis threatened twice, once with a header and then with a shot that Van der Sar did well to save.
But United, with Park and Tevez working tirelessly and Ronaldo firing fitfully, were resolutely dogged and held out for over six minutes of stoppage time to win their 12th straight home match in Europe's premier club competition.
Chelsea play Liverpool in the second leg of the other semi-final at Stamford Bridge on Wednesday, starting 1-1 after last week's first leg at Anfield.
Ferguson added: "I couldn't possibly predict who is going to win that one and I honestly don't care who we play in the final. We are there, that is the main thing."
(Agencies via Shanghai Daily April 30, 2008)