Katy Perry's is about to making an astonishing return to the top of the Billboard singles chart, with industry forecasters suggesting her new song 'Roar' will sell 450,000 downloads by the end of the week.

Fellow diva Lady GaGa - who also released her new single 'Applause' this week following a premature leak - is tracking to move around 225,000 downloads, probably enough to take second place.

Both singles were released to digital retailers on Monday and Tuesday (August 12 and 13) and come from Perry's new album Prism (Oct 22) and Gaga's ArtPop (Nov 11).

It seems forecasters have revised as their numbers, given early indications suggested both artists could sell over 400,000 downloads, making it one of the biggest selling weeks of the digital eras. 

Perry's last album, 2010's Teenage Dream, was headed by the single 'California Gurls' which bowed with 294,000 copies. The pop-star is no stranger to big selling singles - 'Firework' shifted 509,000 over the post-Christmas week of 2010, while 'Part of Me' debuted in 2012 to 411,000 copies.

In terms of making history, both 'Applause' and 'Roar' only need to debut with sales larger than 200,000 for it to represent the first time that two songs have sold that many copies in their debut week since last October. On that occasion, three new songs exceeded the milestone, with One Direction's Live While We're Young (341,000), Taylor Swift's Red (312,000) and Adele's Skyfall (261,000).

Katy PerryKaty Perry's 'Roar' Could Sell 450k Copies This Week

Lady Gaga
Lady Gaga At The Chateau Marmont