Dublin's Lord Mayor, Christy Burke, claims representatives of Aiken Promotions have travelled to the US to try and persuade Garth Brooks to go ahead with three shows in Croke Park.
Two other planned gigs were refused a licence last week, sparking massive public outcry.
In response, the star commented that it was "five gigs or nothing", but the promoters say in a statement that was "not an ultimatum, but an expression of genuine concern for his fans".
There is no possibility to amend or appeal Dublin City Council's licensing decision, meaning that three of the gigs can go ahead if Garth himself decides to play.
He stands to lose millions if he pulls out, and there is a high court action lodged against the three gigs.
Mediator Kieran Mulvey is hoping the country singer changes his mind.