Minister for Transport Eamon Ryan has said they cannot be "precise on the year" that the Dublin MetroLink will be built because it has "to go through the planning system."
On Tuesday, the Taoiseach said that 2034 is a "realistic assessment" of when the capital's MetroLink will be delivered.
However the Transport Minister would not confirm what year the long-anticipated underground rail system would be completed.
Speaking on Newstalk Breakfast on Wednesday morning, Minister Ryan said: "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 before it gets through the planning system before we know exactly how long it's going to take to build."
But the Minister insisted that the MetroLink will be built.
He said: "Those reports that it's not coming, that's not true.
"We're going to do everything, we are actually reviewing the entire planning system at the moment to see how can we make it fairer and quicker for everyone.
"And I think that is important because the build cost increases all the time because of the length in delays.
"But people deserve infrastructure quickly so we are looking at how we can improve the planning system and make it more certain for everyone."
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