Celtic have dominated the first half of their Scottish Cup quarter-final replay against Dundee United, with Jason Denayer giving them a 1-0 lead at the break.

United keeper Radoslaw Cierzniak could have been shown the red card after only three minutes when he felled Leigh Griffiths just outside the penalty area, but he survived with just a yellow.

Griffiths volleyed the ball on goal in the 17th minute, but Cierzniak was equal to it.

Celtic broke the deadlock three minutes later as central defender Denayer looped a header into the net after Anthony Stokes's free kick found him unmarked inside the penalty area.

Griffiths then threatened twice from long range but failed to hit the target.

Nadir Ciftci, returning from suspension, finally got Dundee United's first shot on target, but his long-range effort was easily caught by Craig Gordon.

James Forrest was looking to score his second goal in three days against United. He beat John Rankin, who was playing out of position at left-back, and took aim at the United net but Cierzniak scrambled to palm the ball onto the crossbar.