Planning permission for the new children's hospital is not expected before the end of next year.
Health Minister James Reilly said he hopes to have a design team in place within six months and then to secure the green light from planners for the build by December 2014.
The paediatric facility will be built on St James's Hospital in Dublin, is expected to cost more than 484 million euro and open as late as spring 2018.
"Work on developing a detailed project timeline is continuing under a transitional board recognising the urgency and priority attached to the project, as well as its scale and complexity," Dr Reilly said.
"I will also establish a Children's Hospital group comprising the three existing children's hospitals. This is an important step in moving towards the transition of the three hospitals to a single entity."
The long-awaited development has been dogged by delays and wrangling over its location since its inception.
The 6.3 hectare development on the south city hospital campus will be funded in part with 200 million euro of national lottery money.
Some 39 million euro was spent on rejected plans to build on the Mater hospital site.
The St James's facility will merge the three children's hospitals - Temple Street, Crumlin and Tallaght. The original target had been to start construction in 2011 and open by late 2014.
Dr Reilly has also previously admitted that it will cost more than original estimates of 484 million euro.