The lengthy, emotional note explained that Ward had been asked to participate "minimally" at the band's Download Festival set in the UK in June, then later offered the chance to play a Birmingham warm-up show "for free and see how the first show goes" before potentially joining the group at the Download Festival and Lollapalooza.
"I was tempted," Ward wrote, but said he decided against it. "I can't prioritize the Sabbath fans making one show more important than the other. I can't do that. All of you are important. It's all the gigs or none at all. I can't come to Birmingham and 'see what happens' knowing there is a risk of not being able to play Download or Lollapalooza. Again, for me, it's all or nothing.
"I didn't want to make this decision, but I have to be honest and transparent," he added, noting that he holds "no malice" toward the quartet's other original members.
He closed by stating he remains open to a contract with "signable" terms.
The group announced its reunion and a new album last year before Ward initially declared he wouldn't participate under the current terms. In February, Ozzy Osbourne, Tony Iommi and Geezer Butler responded to Ward's announcement with a statement saying "We have no choice but to continue recording without him although our door is always open."
The group has yet to respond to the new remarks. To add to the band's worries, Iommi is continuing his battle with lymphoma, telling fans in a March Facebook note that he'd just finished chemotherapy.