Luton Shelton claimed his first league goal for United moments before half-time but Kevin Lisbie equalised seconds after the re-start.

Inspired by that goal, bottom club Colchester went on to take the lead midway through the second half after Johnnie Jackson's free-kick took a huge deflection off unfortunate defender Chris Armstrong.

But the lead was short-lived and it was Australian midfielder Carney who once again saved his side`s blushes to earn the Blades a point.

The home side started brightest as Mark Yeates' shot sailed over and Karl Duguid's header went wide.

United centre-back Chris Morgan did well to block Clive Platt's goal-bound effort while John White's 18-yard drive flew over the crossbar after the resulting corner was not cleared.

The visitors enjoyed a period of solid pressure towards the end of the half and were rewarded with a timely strike in the 45th minute.

Morgan was the unlikely supplier as his ball found Jamaica international Shelton who took the ball in his stride and calmly stroked the ball beyond Dean Gerken.

However, just 26 seconds into the second half former Charlton striker Lisbie levelled the scores for Colchester when he collected Kemal Izzet`s feed from the left and lashed home the equaliser.

Inspired by Lisbie, the Us were soon 2-1 ahead courtesy of a wicked deflection in the 63rd minute.

Midfielder Jackson will no doubt lay claim to the goal as it was his 25-yard free-kick that struck the unwitting Armstrong as the ball wrong-footed Paddy Kenny in the Blades goal to make it 2-1.

But just a minute later Colchester's defence allowed their concentration to slip and the scores were level once more.

Australia international Carney was on target for the second time in a week when he slammed his left-footed drive home after good work from Stephen Quinn on the left to set up a frantic final period.

Carney, who also scored in the 1-1 midweek draw with Watford, soon made way for United`s 13-goal top scorer James Beattie, who has missed the last seven games through injury, and he almost made an immediate impact in the 74th minute.

The former Everton striker was denied only by a courageous block from Us captain Duguid and Lee Martin`s effort sailed narrowly over following the resulting corner.

Both sides had late chances as Shelton and Jackson both missed the target but the game ended in a deserved draw.