Neath tore up the form book to destroy Swansea's hopes of a domestic double and secure a Principality Cup final appointment with Newport on 13 May.

The Welsh All Blacks outscored their west Wales rivals 3-2 on tries in a classic Millennium Stadium semi-final.

Neath's Tongan centre Dave Tiueti touched down twice in the second half to stun Swansea, who had led 10-8 at the break.

Wing Shane Williams chipped in with 11 points from the boot, while flanker Brett Sinkinson also touched down.

"It was a big win for the club and the fans. Hopefully now we will carry this through," said Neath coach Lynn Jones.

Neath made a superb start, Williams kicking an early penalty and Sinkinson squirting through for a touchdown following concerted forward pressure - although Williams' attempted conversion struck a post.

Trailing 8-3 after the opening quarter, Welsh-Scottish League leaders Swansea shook off their early lethargy when Wales centre Mark Taylor was allowed to dash through the Neath midfield for a try.

Rees converted, giving Swansea a 10-8 advantage at the break, but that advantage was wiped out within six minutes of the restart.

Williams' searing pace took him clear of the Swansea defence on a kick-and-chase surge and when the All Whites infringed he struck an inevitable ensuing penalty.

Another Williams penalty just two minutes later put Neath 14-10 ahead as the Welsh All Blacks scented a first cup final appearance since 1996, when they lost to Pontypridd.

Frantic

Swansea desperately tried to claw back their arrears but were frustrated by some terrific Neath tackling.

Underdogs Neath then launched a scintillating counter-attack that resulted in their second try, even though sin-binned flanker Rowland Phillips was off the field.

Swansea panicked under pressure and when Rees hacked the ball straight to Neath hooker Mefin Davies his footballing skills created a try for Tiueti on the overlap.