By Jon Hurdle

PHILADELPHIA (Reuters) - The U.S. passenger rail network Amtrak has ended talks about building a new commuter rail tunnel between New York and New Jersey and has no plans to restart them, Amtrak said on Friday.

The breakdown appears to put an end to efforts to revive some form of the rail tunnel project, once projected to be the largest U.S. infrastructure project and a potential source of economic stimulus.

Amtrak had been in talks with New Jersey's public transit agency about a possible alternative to the $8.7 billion tunnel that New Jersey Governor Chris Christie killed last month.

But those negotiations broke off during the past week, removing any prospect that the two agencies would cooperate to build a trans-Hudson tunnel, Amtrak spokesman Cliff Cole said

"Exploratory talks that we had with New Jersey Transit are no longer taking place," Cole said. "The door is shut on that particular subject."

He declined to say why the talks had ended.

The tunnel's cancellation formed part of a national debate over whether state and national governments should seek to stimulate a weak economy with major infrastructure projects, or focus instead on cutting soaring budget deficits, as favored by the Republican winners of the mid-term elections.

Christie withdrew $2.7 billion in funding for the tunnel on October 27, saying the cash-strapped state could not afford billions of dollars in likely cost overruns.

The Republican governor, who has closed a record $11 billion budget gap this year, rejected an appeal by the U.S. Transportation Secretary Ray LaHood to keep the project alive.

(Reporting by Jon Hurdle, Editing by Doina Chiacu)