The New South Wales Waratahs beat their Australian arch-rivals the Queensland Reds 18-11 at Brisbane to seal their Super 14 semi-final place.

The Waratahs scored two unanswered tries to lead 12-3 at the break then added two penalties in the second half to reach the last four for the third time in the last four seasons.

They faced the prospect of missing out if they had failed to win but ensured a regular season second place finish behind New Zealand's Canterbury Crusaders to secure a home semi-final in Sydney next weekend against the eventual third-placed team.

"It wasn't pretty tonight but we got away with a win," NSW captain Phil Waugh said.

"We knew it was going to be tough and we've got a lot to work on but it's great to be heading back to Sydney."

Queensland, who were already out of the running for a spot in the play-offs, scored a last-minute consolation try through left wing Peter Hynes to likely end the season in 12th place after finishing bottom last year.

"The boys put in a big effort but we just didn't come away the points because we didn't hold on to the ball long enough," Queensland skipper James Horwill said.

"We've made a lot of improvement this year but we're still not where we want to be so there's a lot of work still to do."

The Waratahs seized control of the match when Dean Mumm crashed over for a 21st minute try after a sustained build-up. Teenage fly-half Kurtley Beale landed the conversion after missing two earlier penalty attempts.

Queensland replied with a penalty from full-back Clinton Schifcofske but the Waratahs struck a vital blow when Wycliff Palu burst through a hole and scored on the stroke of half-time.

The Reds closed to within six points early in the second half with a drop goal from fly-half Berrick Barnes but NSW pulled clear when Beale booted two penalties before Hynes' consolation.

Reuters