New touring rock festival Sonisphere has added Alice In Chains, Avenged Sevenfold and Machine Head as exclusive additions to its line-up for Knebworth House in the U.K. in August.

Sonisphere runs from June 20 to Aug. 2, hitting venues in Holland, Germany, Spain, Sweden, Finland and the U.K.

Organizers claim Sonisphere will be the only U.K. show for Alice In Chains in 2009. The band will take time out from working on their first album in 13 years to play the festival. Comes With The Fall singer William DuVall took over vocal duties for the band's reunion shows in 2006, following the death of Layne Staley in 2002.

The inaugural event will also be Machine Head's only outdoor U.K. festival appearance, having already announced several indoor shows with Metallica in Nottingham, England.

Also announced for the Knebworth shows are Irish rock stalwarts Thin Lizzy and newcomers the Sword, although organizers have not yet revealed on which days the newly announced bands will play. The Knebworth shows take place on Aug. 1 (headlined by Linkin Park) and Aug. 2 (Metallica headlining).

Meanwhile, Lamb of God and Mastodon have signed on for every Sonisphere date.

As previously announced, Metallica will headline all dates except Aug. 1. It will be Linkin Park's only U.K. show in 2009. More acts are expected to be announced tomorrow (Feb. 25).

Kilimanjaro Live CEO Stuart Galbraith and Metallica's long-time booking agent John Jackson (K2 Agency) launched Sonisphere on Feb. 9. It is being viewed as a direct rival to Download Festival, which is held June 12 to 14 and promoted by Live Nation -- Galbraith's former employer.

AEG, which backs Kilimanjaro, is also supporting Sonisphere.