Shatner will sing the theme song from his 1960s series Star Trek

They will sing themes from classic TV series, while the audience and viewers will get to vote for the winner.

In the contest - which has been dubbed Emmy Idol - Shatner will duet with opera star Frederica von Stade to sing the song from Star Trek.

Talk show host Ellen DeGeneres will host the Emmys on 18 September.

It will be held at the Shrine Auditorium in Los Angeles.

Solo singer

Megan Mullally - who plays Karen in Will & Grace - will also take to the stage in the Emmy Idol contest to sing a duet with Trump to sing the theme to the 1960s comedy Green Acres.

CSI's Gary Dourdan will duet with R&B artist Macy Gray to sing their version of Movin' On Up from The Jeffersons.

Will & Grace's Megan Mullally will also sing in Emmy Idol

Kristen Bell, from Veronica Mars, will be the only solo performer, with her version of the Fame theme.

"There are certain television theme songs that are nearly as memorable as the shows connected to them," said Ken Ehrlich, the ceremony's executive producer.

"By jogging memories as well as creating wonderful moments by having them performed on this year's Emmy show, we think we're giving viewers one more reason to tune in and be entertained."

Among the presenters for the Primetime Emmy Awards ceremony are Halle Berry, Kiefer Sutherland and Charlie Sheen.