By Hilary Russ

NEW YORK, Nov 17 (Reuters) - A regional transportation authority for New York and New Jersey on Thursday approved the formation of a municipal corporation to oversee construction of Amtrak's massive $24 billion Gateway rail transportation project.

The Gateway Program Development Corporation will be an entity within the Port Authority of New York and New Jersey to oversee the project, which stretches from Newark to Manhattan and includes digging new train tunnels beneath the Hudson River which separates the two states.

The corporation, first proposed in 2015, is being led by John Porcari, an executive at consulting firm Parsons Brinckerhoff and former deputy secretary of the U.S. Department of Transportation.

"This is a really important step forward," Porcari said following Thursday's formal approval from the Port Authority Board of Commissioners.

With its official formation, the corporation will be able to apply for and accept up to $6 billion in low-cost loans under federal railroad and other transportation infrastructure programs.

The corporation will also be able to fill positions, a process that will begin by borrowing people from the Port Authority, the national railroad company Amtrak and NJ Transit, Porcari said.

"There is no schedule. It is a question of finding the right people," he said.

Federal officials agreed to split funding for Gateway with the states of New York and New Jersey. But critics have questioned the states' ability to pay for the project.

The new tunnels in particular are considered one of the most important - and urgent - rail projects in the United States.

The existing tunnel, built in 1910, transports nearly 90,000 commuters into Manhattan each day via NJ Transit alone. It was badly damaged in 2012 when Superstorm Sandy flooded the rails and concrete encasements with saltwater and left behind a corrosive residue.

Asked whether president-elect Donald Trump would be good for the project, Port Authority officials ran down a list of supporting factors, including that both Trump and his Democratic rival Hillary Clinton had proposed major infrastructure spending.

"I believe President-elect Trump will pursue that," Port Authority Chairman John Degnan told reporters. "The important thing for us is to get shovel-ready projects ready to take advantage of this."

(Editing by Daniel Bases and Matthew Lewis)