Green Day's cover of John Lennon's track "Working Class Hero" is now available for preview or purchase via iTunes. As announced in early March, the song is the second high profile cover from the band, as they previously worked with U2 to record a song to benefit Katrina victims.

The band is also producing a video with director Samuel Bayer, Bayer was also responsible for the band's videos from American Idiot. Shooting is expected to begin this week.

This cover, along with others from Black Eyed Peas, The Cure, Jack Johnson and Willie Nelson will appear on Instant Karma, a new benefit for Amnesty International's campaign to end the Darfur genocide. Though the United Nations has not been willing to describe the Darfur conflict as a genocide, it is well established that at least 400,000 people have been killed, with an addition 2.5 million displaced by the conflict between the Janjaweed and Fur, Zaghawa, and Massaleit ethnic groups.

You can preview or purchase the song via this link.