The FAI has given the Taoiseach its full backing in the Stadium Ireland row, calling it "the most positive development for Irish sport in the history of the State".
In a statement released this afternoon, the FAI said Ireland needs a second large capacity stadium other than Croke Park to meet the needs of both soccer and rugby.
Lansdowne Rd does not have the capacity required by either sport, it added.
The FAI admitted the costs of the proposed stadium - set by the government at £350m, but estimated by other sources as far higher - are "high, but affordable and worthwhile".
The statement concluded by calling on sporting organisations around the country to unify in pressing the government to begin construction of the Campus Ireland.