Proposals for the highly ambitious Dart underground project are set to be parked, as the Coalition puts the finishing touches to its multi-billion-euro capital spending spree.
The ambitious project would complete the country's first underground transport network.
It has a deadline of September 24 for Compulsory Purchase Orders (CPOs) to be carried out along the proposed route.
But sources have indicated that the proposed €4bn project will be "sacrificed" due to funding constraints and concern among some ministers that the capital plan will be perceived as focusing too heavily on Dublin.
The Government's intentions surrounding the Dart have been in doubt for many months, after Transport Minister Paschal Donohoe said private rather than public funding could be used to build a high-capacity transport system in the capital.
Last year, a total of 25 public transport schemes were identified and assessed, with the list then being whittled down to six.
The different options considered for funding ranged from bus rapid transit - where buses travel on dedicated road space - a reworked Metro North, extensions to the Dart network and a new Luas line.
Mr Donohoe is now expected to be given the green light for the expansion of the Luas between Dublin city centre and the airport.
"There simply isn't the money for both projects. As is always the case with the capital plan, something has to give," said a source.
A spokesperson for Mr Donohoe declined to comment.
The overall proposals contained in the €3.5bn capital plan are due to be discussed by the Economic Management Council (EMC) before being given final Cabinet approval within the next fortnight.
The plan will focus heavily on the justice system, with hundreds of millions of euro being used to revamp the Garda IT system, following the hard-hitting and critical Garda Inspectorate report.
The report highlighted the absence of up-to-date technology as a serious issue.
Health Minister Leo Varadkar is seeking significant funding to improve HIQA facilities, while a substantial cash pile will also be set aside for flood relief and the establishment of a single national property database.
As previously revealed by the Irish Independent, Mr Donohoe warned Public Expenditure Minister Brendan Howlin that failure to invest €300m a year in the transport system would raise the prospect of roads and other infrastructure falling into disrepair.
Mr Donohoe's officials have reported a deterioration of road quality in rural areas, partially as a result of the growth of the dairy and timber industries.