Gov. Christie said New Jersey might be forced to cancel an $8.7 billion commuter-rail tunnel to New York after the federal government estimated the project could cost as much as $5 billion more than projected.

"I don't have the money to pay for going $2 billion to $5 billion over budget," Christie said Tuesday during an interview on Bloomberg Television in New York. "We need to examine what the real cost of that tunnel is going to be. I like the project and think it's good for the region, but I can't spend money I don't have."

Christie called a 30-day halt to work on the project this month to assess the cost. The conduit under the Hudson River would serve a new station beneath Manhattan and is meant to double the number of commuter trains that can travel to New York at peak times.

The governor said that his administration had spoken to the U.S. Transportation Department about the possible overrun and that he was willing to move ahead if the federal government assumed more of the cost. Christie said he would release a plan next month on how to deal with the state's infrastructure and replenish its Transportation Trust Fund, the roadwork account set to run out of money for new projects next year.

Christie's comments came as a Monmouth University survey released Tuesday showed 44 percent of registered voters approve of his job performance, compared with 45 percent in July. His disapproval among respondents declined to 40 percent from 43 percent. The poll has an error margin of plus or minus 3.5 percentage points.

New Jersey broke ground in June on the train tunnel. Officials said the passageway would create 6,000 construction jobs and ease delays for hundreds of thousands of commuters.

The project is "significant and has a ripple effect on the economy," said U.S. Sen. Robert Menendez (D., N.J.).

"Unfortunately, our governor is in the midst of trying to cannibalize the state contribution," he said Tuesday in Washington during a Senate Banking Committee hearing on President Obama's proposal to create a U.S.-backed bank to increase infrastructure spending.

U.S. Transportation Secretary Ray LaHood and Christie discussed the project and work stoppage during a telephone call Sept. 16, said Brian Farber, a spokesman for the Federal Transit Administration, part of the Transportation Department.

"Given that this project represents the single largest transit investment ever made by the Federal Transit Administration, the secretary and governor agreed to have staff work together to further refine the estimated cost of the entire project," Farber said in an e-mail Tuesday.

James Weinstein, executive director of NJ Transit, told state lawmakers there had been talk in Christie's administration of using $2.5 billion in state money earmarked for the project to replenish the transportation fund.

At a news conference in Bayonne on Tuesday, Christie said decisions about the tunnel and trust fund must be separate.

"This is the worst-case scenario for a lot of New Jerseyans," said Zoe Baldwin, New Jersey director for the Tri-State Transportation Campaign, which advocates for transit investment in New York, New Jersey, and Connecticut.

"If Gov. Christie takes that money and uses it as a short-term fix for the Transportation Trust Fund, he's just kicking the can down the road," Baldwin said.

Christie also said during the television interview that he expected his proposals to reduce pension benefits for current workers to pass the Democratic-controlled legislature in "the next 90 days," and that he did not expect the cuts to affect consumer spending.

The governor this month called on lawmakers to roll back a 9 percent benefits increase approved in 2001 and indefinitely freeze cost-of-living adjustments to reduce the state's $46 billion pension deficit. He proposed making workers cover 30 percent of their health-care costs, up from about 8 percent now.

Senate President Stephen Sweeney (D., Gloucester) said he would block Christie's pension proposals unless he paid into the fund. Christie skipped a $3.1 billion pension payment this year, saying he wouldn't put money into a "broken" system.

In a radio interview on Monday, the governor said he intended to reduce state income taxes within two years to stimulate the economy.

New Jersey is "the failed experiment of the last decade" because its income-tax increases didn't result in higher revenue, Christie said on Tuesday.

The state faces a $10.5 billion deficit next year because of higher costs, nearly matching the one Christie closed in his current $29.4 billion budget, the independent Office of Legislative Services said in July.

Christie has said that estimate, which assumes the state funds all programs and obligations, was not realistic.