The European Investment Bank has given approval in principle for a €500m loan for Dublin's Metro North project.
It said the bank's directors had signed off on the massive package for the public-private partnership project.
Transport Minister Noel Dempsey said the move was an important signal of confidence in the project.
"Metro North is now well on track for delivery in 2016," he said. "The oral hearing before An Bord Pleanala on the railway order application for Metro North concluded in March this year. The decision is anticipated this summer."
The project involves the design, construction and maintenance of a light metro system serving an 18.8km northern corridor from Dublin city centre to Fingal, via Dublin Airport.
Plutarchos Sakellaris, of the European Investment Bank, said that "the Metro North project represents a significant contribution to sustainable urban transport in the greater Dublin area".