The MTA said Wednesday that it cannot afford to pick up any cost overruns from extending the number 7 line to Manhattan's West Side, possibly putting the project in jeopardy.

The city had agreed to pick up the entire tab for the estimated $2.1 billion project. But it could wind up costing much more, and the MTA says it won't make up the difference.

The project would extend the 7 line to 34th Street and 11th Avenue. But the possible construction of a subway stop at 10th Avenue and 41st Street would add another quarter-billion dollars to the original estimate.

The mayor's office says the city has no plans to put additional money towards the project, and they point out that development in the area will bring the MTA billions of dollars in new tax revenue.

Tunneling was expected to begin this summer.