Dominating against the second-from-bottom visitors, the Blues powered into a 27-3 half-time lead with Martyn Williams, Gareth Thomas and Jamie Roberts helping themselves to tries.

But Ulster, as the did against Connacht last week, fought back in the second half and got within ten points thanks to touchdowns from Ryan Caldwell and Tommy Bowe.

However, a 76th-minute penalty goal from replacement David Flanagan eased the tension for the Blues and sealed their ninth win in ten matches at the Arms Park.

It also maintained Ulster's disappointing form on Welsh soil. The Irish province have now lost on their last nine trips to the Principality and Matt Williams' side never looked like breaking that chain of results.

Williams made six changes to the side that accounted for Connacht, one enforced with hooker and captain Rory Best sidelined with a groin injury.

Former Ireland flanker Kieron Dawson took over as captain and the 20-year-old Niall O'Connor remained in the fly-half hot seat.

Cardiff welcomed back Jamie Roberts and Gethin Jenkins, with the pair having recovered from the ankle injuries they picked up in European action against Toulouse.

David Young's men began their last home game of the season in good fettle with full-back Ben Blair kicking a third-minute penalty.

They followed up with a try on the quarter-hour mark and fittingly it went to their workhorse captain Martyn Williams.

The Wales flanker began the move, taking a lineout ball towards the tail.

He was up in support of Nick Robinson's midfield burst, stretching to a take a pass one-handed from the fly-half before managing to step past Ulster full-back Mark McCrea and cross the whitewash.

Blair added the conversion before O'Connor, who was caught out by Robinson for the try, regained his composure to secure Ulster's opening points with a 20th-minute penalty.

That kick took the Belfast Harlequins' tally for the league campaign to 50 points but Cardiff started to purr before the interval. They got over for two tries in the space of seven minutes.

After Blair had cancelled out O'Connor's penalty with one of his own, strong-running winger Tom James barged his way through on a powerful charge.

James shrugged off tackles from Paul Marshall and Roger Wilson and then offloaded in good time to Maama Molitika who set up Thomas to score close to the points.

Blair added the extras and he also turned Roberts' 40th-minute into a seven-pointer.

It was another fine score from the Welsh region. They showed some great continuity with James and Molitika again involved.

The ball was swung out to the left and then the right and with the Ulster defence stretched, a pass from Deiniol Jones sent Roberts over for his seventh try of the campaign.

Ulster introduced Ireland duo Neil Best and Isaac Boss for the second half and aided by a general improvement from the pack, the province's game picked up.

The Blues lost their way in the sweeping rain and Ulster were able to eat into the hosts' lead.

Before being replaced, scrum half Paul Marshall was held up short. Off the ensuing ruck, lock Ryan Caldwell was shunted over by his fellow forwards for a 54th-minute try.

O'Connor converted but Caldwell was the man singled out by referee Andy Macpherson, four minutes later, after the Ireland 'A' international infringed at a ruck.

Caldwell saw yellow for his indiscretion and the Blues, who had got back into Ulster territory thanks to a Thomas break, looked poised for a bonus point try.

Ulster's defence was stubborn and the Blues were left down by some poor handling as a fourth try never came.

On 74 minutes, Ulster cut the gap to 27-17 when Rob Dewey and Andrew Trimble hacked the ball upfield, out of their own half, and Tommy Bowe was first to the bobbling ball as it went over the Blues' try line.

Television match official Tony Rowlands confirmed the grounding and with O'Connor converting, Ulster were only ten points with enough time left on the clock.

Nonetheless, the Blues were able to make the game safe two minutes later with Flanagan's successful penalty ending Ulster's game effort.