The Minister for Transport Mr Cullen hopes that work on joining Dublin's two Luas lines in the city centre will be "well under way" by 2007, his spokesman said yesterday.
In a significant change in the transport priorities set by his predecessor, Mr Séamus Brennan, Mr Cullen has put the Luas link at the top of his list.
Mr Cullen's spokesman said yesterday that the Minister had already discussed his plan with the Taoiseach and the Minister for Finance, and officials in the Department of Transport were currently preparing proposals for Cabinet on the issue.
He would not set a date for when these proposals would be ready, but it is hoped that they will go to Government early in the New Year.
A spokesman for the Rail Procurement Agency (RPA) said yesterday that if the Government did decide to proceed, they could begin the necessary consultation process on the new link in the New Year.
This could lead to a Railway Order being made by next summer. Other aspects of the planning and preparatory process would mean work might not start until at least a year later - after summer 2006.
The construction work itself would then take some 18 months and, according to the RPA, would cost under €100 million. Mr Cullen's proposal, if approved, could ensure work is under way in the capital before the next general election.
Mr Brennan championed the proposal for a Metro link from the city centre to Dublin Airport during his time in the post.
However, this is seen as too costly by many in Government, and the Taoiseach, Mr Ahern, said last week that it would not be built by 2007 as originally promised.
A spokesman for the Minister insisted yesterday that the ambitions of Mr Brennan to build a Metro link from the city centre to Dublin Airport had not been shelved in favour of the completion of the Luas link.
However, the Taoiseach conceded last week that Mr Brennan's ambition to build a Metro by 2007 - at a cost of €3.4 billion - could not be realised.
The RPA has already set up a team to carry out preliminary work on the costing, technical requirements and environmental impact of such a project.
It was always intended that the two lines would join. However, following a review of the project, ordered by former minister for transport Mrs Mary O'Rourke, it was decided not to link them.
A track joining the two Luas lines would run from St Stephen's Green down Dawson Street, around College Green, along Westmoreland Street and over O'Connell Bridge, to link with the red line at the Abbey Street/O'Connell Street junction.