MANCHESTER, England — Defending champion Manchester United defeated Arsenal 1-0 Wednesday night in the first leg of an all-English European Champions League semifinal, getting a 18th-minute goal from defender John O'Shea.

Michael Carrick beat a defender on the left off a corner kick, and his cross deflected off Alex Song to the unmarked O'Shea, who drove the ball past goalkeeper Manuel Almunia into the roof of the net.

The teams meet against Tuesday at Emirates Stadium. The winner advances to the May 27 final in Rome against Barcelona or Chelsea, who tied 0-0 Tuesday in Spain.

Manchester United defeated Chelsea 6-5 on penalty kicks following a 1-1 tie in last year's final at Moscow. United already has won this season's FIFA Club World Cup and the English League Cup, and is in control of the Premier League race. United was eliminated by Everton in the semifinals of the FA Cup.

Ryan Giggs made his 800th appearance for Manchester United. The 35-year-old midfielder, who made his United debut un March 1991, replaced Anderson in the 67th minute.

Arsenal, fourth to first-place United in the Premier League, was without injured Robin van Persie and Andry Arshavin, who was acquired in January and is ineligible to appear for the Gunners in the Champions League.

Almunia tipped away Wayne Rooney's looping header in the second minute, then saved Carlos Tevez's close-range shot off a cross from O'Shea.

Almunia saved a close-range header from Cristiano Ronaldo as well as his follow-up shot and then raced off his line to dive at the feet of Tevez as United threatened again.

Although Arsenal had a spell of possession before halftime, the Gunners did little to worry United goalkeeper Edwin van der Sar, with defenders Rio Ferdinand and Nemanja Vidic firmly in control of striker Emmanuel Adebayor.

Adebayor had a powerful shot that just cleared the crossbar in the second half, and Ronaldo's 25-yard drive hit the crossbar.