Shirley Bassey is to return to north Wales for the first time since 2003

They are the first acts to be confirmed for the annual event, launched by the Welsh opera star in August 1998.

In 2005, more than 30,000 tickets were sold and organisers say the August Bank Holiday event at the foot of Snowdon brings �1.5m to the local economy.

Terfel said he was delighted with the big name bookings.

The Irish band will open the four-day 2006 festival on the Friday night, which is held in a spectacular setting on the Faenol Estate, near Caernarfon.

Cardiff-born Dame Shirley will headline the Sunday night.

Westlife will open this year's festival

Westlife burst onto the UK music scene seven years ago at about the same time Terfel's festival was launched.

Dame Shirley will be performing in north Wales for the first time since she sang at the Llangollen International Eisteddfod's gala in 2003.

Terfel said: "I'm delighted to be joined this year by Dame Shirley Bassey and the boys of Westlife - they are without a doubt among the brightest stars of the popular music world"

The singer said he was "very excited" by the festival line-up taking shape for the Saturday night classical gala.

"I'm keeping cards close to my chest until we finalise discussions, but look forward to introducing some stunning new classical artists and some internationally-renowned opera stars in Wales," Terfel said.

"It's going to be a wonderful and very memorable festival."

'Such as success'

The Faenol Festival has grown in size and stature since its launch, now attracting visitors from as far away as the USA.

Last August, Italian tenor Andrea Bocelli, Van Morrison and Katherine Jenkins were among the draws.

Also last year, the festival expanded from a three-night to a four-night format.

Terfel said it was "such a success that we're sticking to it".