Shunsuke Nakamura and Scott McDonald hit the woodwork in the first half before United midfielder Craig Conway missed a sitter from six yards out when he headed over with only Artur Boruc to beat.

The Tims could not find a way past a resolute Tannadice defence who now look forward to Sunday's CIS Insurance Cup final against Rangers at Hampden.

The jeers rang out around Celtic Park at the final whistle with the realisation that the Ibrox club are three points ahead and with a game in hand as the SPL title race hots up.

In the third minute midfielder Aiden McGeady crossed from the left to find McDonald who helped the ball on to the unmarked Nakamura at the back post.

The Japan international carefully curled his low, left-footed drive from 14 yards past United keeper Lukasz Zaluska but watched the ball clip the outside of the post before speeding past.

Nakamura turned provider when he skipped past Danny Grainger on the right to throw the ball up to the back post where the stretching Georgios Samaras headed over the bar.

United forced a couple of corners midway through the first half, to no avail, and although the champions remained on top, the United were not being asked too many difficult questions in defence.

In the 25th minute a back-header by Andreas Hinkel at the near post from Nakamura's corner left Zaluska grateful to push the ball away for another corner but again the United men held firm.

Next to threaten was Celtic skipper Stephen McManus who flicked a Nakamura free-kick wide of the far post before McDonald took a Scott Brown pass inside the United box on the half-hour mark and rattled the outside of the post with a low drive from 12 yards.

But in the 38th minute the visitors should have taken the lead when Kovacevic's cross from the right found Craig Conway six yards from goal. The United midfielder somehow headed over the bar with just Hoops keeper Boruc to beat and clasped his hands to his head in frustration.

In the 53rd minute Nakamura's whipped-in free-kick from the left was flicked on by the head of Brown through a ruck of players in the six-yard box but found no takers.Despite their possession, the home side were struggling to breach the well-drilled United rearguard and just after the hour mark Jan Vennegoor of Hesselink and Barry Robson replaced Samaras and Evander Sno respectively.

United, growing in confidence, had a more than decent penalty claim when Robson appeared to charge down Prince Buaben's drive with both hands inside the Celtic penalty area.As the tension mounted, McManus had a low drive saved by Zaluska at the second attempt and then McDonald went down rather too easily in the United box after brushing past United stopper Garry Kenneth.

With five minutes remaining Vennegoor of Hesselink drew a good save from Zaluska seconds before he headed a Nakamura cross over the bar from eight yards out.

Celtic: Boruc, Hinkel, Caldwell, McManus, Naylor, Nakamura, Scott Brown, Sno (Robson 62), McGeady, McDonald, Samaras (Vennegoor of Hesselink 62). Subs Not Used: Mark Brown, O'Dea, Hartley, Donati, Riordan.

Booked: Scott Brown.

Dundee Utd: Zaluska, Kovacevic, Wilkie, Kenneth, Grainger, O'Brien, Robertson (Flood 75), Buaben, Kerr, Conway (Daly 83), De Vries (Hunt 77). Subs Not Used: McLean, Dillon, Dods, Swanson.

Booked: Kenneth, Wilkie.

Att: 45,000

Ref: M McCurry

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