It was not quite the SAS, but Chris Sutton joined with John Hartson at Tannadice yesterday to send out a warning to Blackburn Rovers ahead of Thursday's Uefa Cup tie.

The former Ewood Park striker had to be content with a place in midfield to accommodate Hartson and Henrik Larsson in Celtic's attack, but that enhanced the aerial threat and both players scored headers to keep Celtic in touch with Rangers at the top of the Scottish Premier League.

Celtic were not given a comfortable time by the home side, whose resistance forced the champions to hang on to Hartson's 13th-minute lead until Sutton struck two minutes from the end.

Hartson must love playing against Dundee United. His goal yesterday maintained his record of scoring against them on every meeting since his move from Coventry City. Now he returns south in midweek desperate to be given a chance of starting by Martin O'Neill. "If I am playing well and scoring goals then I would expect to play every week," Hartson said.

The day had begun in routine fashion for Celtic when they forged ahead at an early stage. Alan Thompson had taken a quick free-kick to Steve Guppy and the former Coventry winger picked out his colleague as Hartson rose to guide a header past the goalkeeper Paul Gallacher.

Dundee United almost equalised in the 29th minute, but the Celtic keeper, Robert Douglas, made a superb reaction save to push away a header from Jim Lauchlan.

Celtic were then denied a clear penalty when Mark Wilson brought down Larsson in the box, but the Swede almost took revenge with a wonderful curling free-kick a few minutes later.

A second half peppered with vendettas failed to bring any further scoring until Derek Lilley fouled Larsson to concede the free-kick with which Thompson picked out Sutton, who rose to plant a header wide of Gallacher.

Goals: Hartson (14) 1-0; Sutton (88) 2-0.

Dundee United (3-5-2): Gallacher; Lauchlan, Wilson, McCracken; McCunnie, Miller, Easton, McIntyre, Paterson (Smart, 71); Lilley, Thompson. Substitutes not used: Combe (gk), Duff, Hamilton, O'Donnell.

Celtic (3-5-2): Douglas; Valgaeren, Balde, Laursen; Sylla (Agathe 69), Sutton, Lennon, Thompson, Guppy; Hartson (Lambert, 82), Larsson. Substitutes not used: Gould (gk), Maloney, Crainey.

Referee: J Underhill.

Man of the match: Hartson

Attendance: 10,664.