The sisters told bandmates Melanie Blatt and Shaznay Lewis that they no longer want to work with them.
Insiders say that a statement is prepared in case talks fail, and the girls do split up.
The band, who have a world tour coming up, were voted Best Pop Act at last year's MTV Europe Music Awards - but, despite their success, they have been dogged by conflict. And Shaznay and Melanie are jealous of all the attention the sisters get. Melanie and Shaznay will probably try to continue as All Saints. The sisters are likely to take some time out.