With the Ibrox side drawing 0-0 at Motherwell earlier in the day, a win of any sort would have taken Tony Mowbray's side two points clear at the top.

Tannadice striker David Goodwillie drove the visitors into the lead in the sixth minute to stun the home crowd.

When Celtic striker Scott McDonald equalised in the 17th minute by heading in a Danny Fox free-kick from close range, it looked like Celtic would go on to complete their comeback but they came up against a United side who were well worth the point.

Allan McGregor came to the rescue of 10-man Rangers with a superb late penalty save to prevent the champions slumping to defeat against Motherwell.

Madjid Bougherra was dismissed for dissent after conceding the spot-kick but McGregor ensured Rangers left Fir Park with a point when he blocked from Jim O'Brien.

However, his efforts were not enough to maintain Rangers' 100% record in the SPL ahead of Wednesday's Champions League opener against Stuttgart.

St Mirren drew 1-1 at home against St Johnstone, and had goalkeeper Paul Gallacher to thank as the visitors rued a series of second-half misses.

Gallacher pulled off great saves from Murray Davidson and Chris Millar while Steven Milne missed a sitter as St Johnstone had to make do with their third draw of the season.

Jody Morris had driven home for the visitors four minutes after Billy Mehmet's penalty gave St Mirren a 33rd-minute lead.

Hearts' SPL match against Kilmarnock was called off due to the visitors being stuck in long tailbacks caused by a lorry fire on the M8 motorway which would have severely delayed their arrival at Tynecastle.

The match was rearranged for Tuesday night, with a 7.45pm kick-off.