The Taoiseach has said he is more sympathetic to concerns over the proposed M3 motorway than over other roadway proposals because "at least this time it is about our heritage".
In previous cases controversy arose over "swans, which are breeding very well and snails, which have moved on", he said.
Mr Ahern said the Government would not "call" a decision on the controversial proposed route through the Tara-Skryne Valley until all the reports from archaeologists were received.
But he said there was no better alternative route.
Labour leader Mr Pat Rabbitte called for the Government to abandon this route because it would be "bogged down in litigation for 10 years".
Mr Ahern said, however, that "if there was an easy route, right or left, I would take Deputy Rabbitte's view that we should cut our losses and build on it, but there is not an easy route to the right or left" of the current road plan.
He recalled the controversy over the Swords bypass in the mid-1990s.
The Tara motorway "is more significant, and I would like the archaeologists to provide the Government with a clear report on what they honestly believe, and perhaps then the Government can call it".
Mr Ahern said he was aware of comments made by Mr Seán Haughey (FF, Dublin North-Central), the new chairman of the environment committee, but pointed out that Mr Haughey had also said he would visit the site.
