The Swedish band launched a new website on Thursday morning titled "Abba Voyage", asking fans to register interest in a new project.
It is expected to be a long-gestating "hologram tour" that Abba initially announced in 2016.
The band are also expected to release five new songs to accompany the show.
The quartet - Agnetha Faltskog, Anna-Frid Lyngstad, Bjorn Ulvaeus and Benny Andersson - returned to the studio in 2018, promising two new songs later that year.
Those tracks, I Still Have Faith In You and Don't Shut Me Down, have been repeatedly delayed - and the band are now planning to release five tracks to thank fans for their patience.