TRENTON - Gov. Christie said he would consider restarting a stalled New Jersey-New York rail tunnel if someone else helped pick up the tab. Otherwise, he said, he's comfortable walking away from the $9 billion project.

Christie killed the country's largest public-works project because of anticipated cost overruns, but agreed to a two-week reprieve at U.S. Transportation Secretary Ray LaHood's urging. The Republican governor's transit team has until the end of the week to identify financial options that could keep construction on track.

"They're going to come to me Friday," Christie said at a news conference Monday. "If there are ways that other people are going to be responsible, I'm happy to look at it. If it ends up that New Jerseyans are the ones on the hook for $2 billion to $5 billion for a tunnel to the basement of Macy's, I say, 'No, thank you.' "

Cost projections have nearly doubled. The tunnel started at $5 billion in 2005, and federal officials put the price tag in recent months at $9 billion to $10 billion. Christie recently estimated the cost at $11 billion to $14 billion, though Sen. Frank Lautenberg said that figure was likely far too high.

Under the project's current financial structure, the federal government and the Port Authority of New York and New Jersey are each contributing $3 billion. New Jersey's share is $2.7 billion plus overruns.

"This is a mathematical equation," the governor said. "If it's $2 billion to $5 or more billion over, I'm not doing it. I'm not letting the people of New Jersey be responsible for a never-ending bill."

He referenced Boston's so-called Big Dig, a city tunnel project whose nearly $15 billion cost far exceeded the original estimate.

The link under the Hudson River, which is under way and expected to be finished in 2018, would double rail capacity into and out of Manhattan, taking 22,000 cars off the roads daily and adding 6,000 construction jobs in an industry where unemployment is hovering at around 50 percent.

Christie declined on Monday to specify what type of financial arrangement he was looking for. So far, New York City and state have not offered to contribute to the project.

Lautenberg said he had spoken with an investment firm about the tunnel's value. He said he had not ruled out a public-private partnership and anticipated there would be interest in peripheral investment in nearby retail, buildings or hotels. However, he said it was impossible to talk with possible investors unless Christie agrees to restart construction.

Proponents began ramping up public support for the project.

New Jersey Public Interest Research Group on Monday started a public campaign to pressure Christie into moving ahead with the tunnel. The group delivered to Christie about 200 letters from commuters laying out how train congestion made their commutes worse and how a tunnel could improve that.

"I have been commuting to New York since 1971," wrote Frances Duggan of North Arlington. "A trip that took 20 minutes in 1971 takes at least 40 minutes and frequently runs to an hour or more. A new tunnel would shorten my trip and allow me to spend more time at the nursing home with my mother."

PIRG organizer Jacob Koestier acknowledged, however, that the consumer advocate group did not have a way to pay for the tunnel.

Charles Wowkanech, president of the New Jersey state AFL-CIO, announced a rally for Tuesday at the tunnel site.