The next stop for New Jersey in its debt collection fight with the federal government may be federal court.

On Friday, the Transportation Department flatly rejected the state’s arguments for refusing to repay $271 million that was spent on a project, canceled last year, to build a pair of rail tunnels under the Hudson River. The message to Gov. Chris Christie was blunt: Repay now or we will collect the debt the hard way. Plus interest.

In a letter to New Jersey’s senators and representatives in Congress, Ray LaHood, the transportation secretary, warned that his department had “many tools under the Debt Collection Act to recoup the lost federal taxpayer funds, including withholding future state funding from a wide variety of sources.” But “in consideration of the current economic challenges burdening New Jersey,” Mr. LaHood added, he hoped to “develop a workable payment schedule” and avoid having to resort to those collection methods.

Mr. LaHood should not expect to find a check in the mail any time soon. Mr. Christie, who was in Massachusetts on Friday to speak at Harvard University, declared in January that “we are not paying the money back.”