For some City Council members, Mayor de Blasio’s streetcar leaves much to be desired.

At an oversight hearing Thursday, they made administration officials defend the need for and viability of the proposed waterfront trolley, known as the BQX, a project that has hit roadblocks since Mayor de Blasio proposed it three years ago.

“$3 billion at this moment? And how will we get that money in the city to actually build this out?" Councilman Antonio Reynoso, a Brooklyn Democrat, said. "The timeline by which this will be built is another concern and then, the last one is alternatives.”

Councilwoman Laurie Cumbo, a Brooklyn Democrat, raised concerns about gentrification.

“Any place where there are multiple train hubs, an ease to get to work or ease to get to wherever you’re going, that becomes a destination for a people that want to move into the community and displace others," she said.

The BQX would run along 11 miles of the Brooklyn-Queens waterfront, from Red Hook to Astoria, with 30 stops and a projected 30,000 riders a day.

But the estimated cost has grown $200 million, to $2.7 billion, even as the route has been cut five miles, about 30%.

And after projecting the line would pay for itself, through taxes generated by rising property values, City Hall now says it would need the feds to foot half the bill.

Still, administration officials told the hearing the streetcar line would do what a simple bus line would not: boost property values and tax receipts, while also helping link communities underserved by the subway.

"The Brooklyn-Queens Connector is intended to stitch together the gaps left by the subway system," Seth Myers, director of project implementation at the city Economic Development Corporation, said.

Ahead of the hearing, public housing tenant leaders and union workers rallied outside City Hall, a show of support organized by the Friends of the BQX, a real estate-backed group seeking to jump start the seemingly stalled project.

"Obviously, Friends of the BQX would love to see it move along faster but it is moving," said Jessica Schumer, executive director at Friends of the BQX.

But the project is not exactly on the express track.

An environmental review is not expected to be completed for 15 months, and the first street cars would not begin running until 2029 - and that's only if the funding can be secured.