VIENNA (AP) — Mary J. Blige, Chris Brown and Natalie Cole will be among the top artists performing at a Sept. 26 Michael Jackson tribute concert in Vienna, organizers said Tuesday.

But they left open the possibility that major stars such as Madonna might still be part of the show that will take place outside a 17th-century palace in the Austrian capital.

“Just hold your horses!” Jackson’s brother Jermaine told reporters at a packed news conference in Vienna’s city hall.

Event promoter Georg Kindel said that up to 25 performers are expected to participate in concert that is being billed as the main global tribute for the King of Pop, who died June 25 in Los Angeles. More names will be unveiled later this week in London and Berlin, Kindel said.

Sister Sledge, Akon, Angela Bassett, and the Germany-based boy band US5 also are among the 13 artists confirmed so far, Jermaine Jackson said. In addition, Jackson’s original band and dancers will take part.

“We’re very excited — the list is growing more and more,” Jermaine Jackson said, adding that “many major Bollywood names” and artists from the Middle East also would be involved.

All the artists will play some of Jackson’s greatest hits at the concert, including “Thriller,” ‘’Billie Jean,” ‘’Black or White” and “Bad.”

“We will honor on this night not only the musician and artist Michael Jackson but also the humanitarian,” Kindel said. “He’s really someone who changed the history of music.”

Jackson’s family and children — as well as 65,000 fans — are expected to attend the tribute to be held on a large stage with a crown on its roof and two runways in front of Vienna’s former imperial Schoenbrunn Palace, one of the Austrian capital’s top tourist attractions, Kindel said. A “significant portion” of the proceeds from the event will be donated to charity, he added.

Over the course of the evening, Jermaine will sing a duet with his late brother, with video of Michael likely to be projected onto nearby walls, organizers said. All artists will sing either “Heal the World” or “We are the World” as a grand finale.

Bassett, an actress, will present one part of Michael Jackson’s life, a statement said.

When asked why stars such as Madonna and Whitney Houston — mentioned in Austrian media reports — were not on the list made public Tuesday, a defensive Kindel stressed the list of performers was still not set in stone. “This is not the final lineup — maybe some of the names you mentioned you will hear within the next couple of days,” he said.

A sly Jermaine Jackson, meanwhile, acknowledged in response to another question that organizers were “in contact” with artists such as Madonna, Stevie Wonder and Diana Ross.

Jermaine Jackson has said Vienna was chosen as the venue because his brother “loved castles,” and because Jermaine was impressed with how a smaller tribute held in July outside a mothballed nuclear power plant was organized.

“The beauty of the city is what just really knocks us out because it’s just a wonderful setting,” to keep Michael’s legacy alive, Jackson said.

Tickets went on sale last month.

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