The Public Expenditure Minister says Dublin's planned MetroLink project will enter the statutory planning phase in early 2022.
This comes amid reports that the project could be pushed out to 2034.
Michael McGrath was speaking ahead of the Government's launch of its revised, €165bn National Development Plan (NDP).
The NDP was due to run to 2027, but the Government decided to revise it in part to factor in newer 2030 climate targets.
While it sets out capital spending across the economy, much of the attention will be on transport infrastructure - which is expected to make up €35bn of the €165bn spend over the next decade.
It will see €2 spent on public transport for every €1 spent on roads.
On the MetroLlink, Minister McGrath told Newstalk Breakfast they will be moving ahead with the project.
"The plan for MetroLink, as set out in this new National Development Plan, is that it will enter the statutory planning process in the first half of next year.
"The funding that we have provided in this NDP will allow the project to move off the drawing board, as such, and into construction.
"You are subject to an approval process, and we all have to acknowledge that.
"Even with the political will, with the budget to back it up you have to get approval.
"And for a mega project of this scale, there are significant steps that have to be gone through in that project development life cycle.
"But a preliminary business case has now been submitted, will be going to Government in the coming months as required under the public spending code.
"And once that is approved, it then commences the statutory planning process - and really much depends on how quickly that journey can be completed.
"And the important thing from the Government's point of view now is to get it into that statutory planning phase in the coming months.
"And I know Minister Eamon Ryan is committed to doing that".
While speaking last week, Minister Ryan said he couldn't give a precise year for when the Dublin Metro would begin operations.
"We will deliver Metro, we can't be absolutely precise on the year because it does have to go through the planning system.
"It has to go to Government first of all, but I'm confident that we'll get it to Government and through Government and approved by Government in the coming months.
"But then it does have to go into a planning system that we've seen in the past does take time, and it's not certain.
"We do have to wait until it gets through the planning system before we know exactly how long it's going to take to build", he said.