A promise of an hourly train service between Belfast and Londonderry has been thrown into doubt.
Infrastructure Minister Chris Hazzard said its introduction depends on his department being able to secure the necessary funding from the Executive.
The campaign for the hourly service got a boost in January with the opening of a passing loop at Bellarena, and it had been hoped it could start in 2021.
People Before Profit MLA Eamonn McCann called the latest response very disappointing.
The Foyle representative uncovered the situation via an Assembly question.
He asked Mr Hazzard why, after the opening of the facility at Bellarena, the hourly rail service from Belfast to Londonderry was still five years from completion.
Mr Hazzard was unable to give a start date, saying it depended on his department securing the necessary funding from the Executive.
"The completion of phase two of the Coleraine to Derry track relay will create the potential for an hourly service between Belfast and Derry," he said.
"The introduction of such a service is dependent upon my department securing the necessary resource funding to subsidise Translink to operate the additional services required.
"This is currently estimated at £1.4m per annum."
Mr McCann said he was concerned by the response. "The fact that the minister feels unable to put a target date in the answer is disappointing and worrying," he said. "We had understood we were talking about 2021, now it seems like it has been pushed off yet again - the can has been kicked down the track by no means for the first time. It is worrying and we will have to keep up the pressure."
Mr McCann went on to compare the £1.4m needed for the hourly train service with how much has been invested in road schemes. The dualling of the A5 is currently projected to cost £850m - up from the original estimate of £560m in 2007.
"The estimate of £1.4m per annum doesn't seem to me to be a vast sum to operate the additional services in the context of transport spending," he said.
"If that is the only reason, it is not a good reason with the sort of sums being made available for road schemes.
A spokesperson for the Department for Infrastructure said: "Just last week, during a visit to Derry, the Minister made clear that he is committed to developing the infrastructure offering in the north west region and is determined to address the long running imbalance.
"As the Minister has said in his response, the completion of the current scheme creates the potential for an hourly service.
"This is something the Minister wants to see happen in the time ahead and is currently examining funding options."