Ministers on both sides of the Border are considering whether they should buy new trains for the Belfast to Dublin railway line.
Stormont MLAs were told Translink and Iarnród Éireann have asked for money to replace existing stock.
The North's Transport Minister Conor Murphy revealed they also want to expand their fleet on the busy cross-Border Enterprise service as part of plans to increase its frequency and reduce journey times.
The governments are pressing to reduce the journey times between both cities from two hours five minutes to one hours 40 minutes.
Mr Murphy confirmed both companies were preparing a business case for the renewed investment to be considered as early as May.
"It has been accepted and proven that where we have made investments in public transport - in railways, in the tracks and the rolling stock- that it has improved the service and has also improved the uptake of the service and passenger numbers have increased," he said.
Mr Murphy said the governments were approached about money for the new fleet at last month's meeting of the North South Ministerial Council (NSMC) Transport Sector in Trim. Co Meath.
Minister for Transport Noel Dempsey and Stormont Environment Minister Arlene Foster held talks with operators about improving the Enterprise service.
"In the longer term interests, on environmental issues - in reducing our carbon footprint - we want to attract more and more passengers onto public transport - onto railway," Mr Murphy told the Assembly. "So I think we will continue to make the case for investment."
The Newry And Armagh MP said the business case for the new trains could be ready by the next NSMC Transport meeting in May.