A consortium of hospitals in Dublin has come together to support revised plans at the Mater hospital site for a new National Children's Hospital.
An Bord Pleanala rejected the original plans at the Mater - but those have now been redrawn on a lower scale.
The Mater, Temple Street Children's Hospital and the Rotunda Maternity Hospital argue that a tri-located hospital will provide the best services, and that the project is "ready to go" on the Mater site.
The group is also warning that the selection of any other site for a children's hospital will mean a delay of at least two and a half years.
"The Mercy order has offered to give the use of the original Mater Public Hospital so that the children's hospital could be reduced in height without losing any space" said Donal Walsh, chairman of the board at the Mater.
"We believe that these new solutions will address all the concerns raised by An Bord Pleanala".
"Importantly, there would be no site acquisition costs on the Mater site, it's ready to go," he added.