The cash-strapped MTA’s capital plan must be approved by its board in three weeks — but some board members are still yet to see it.

“I don’t see why we haven’t seen it yet. It’s going to be a very complex document,” non-voting rider rep Andrew Albert told The Post on Monday. “The board certainly needs to have ample time to look it over.”

Albert’s comments came as transit advocacy and good government groups rallied outside the MTA’s Manhattan headquarter to rail against what they see as a lack of transparency in the roll-out and approval of the plan, which spells out the agency’s next five years of construction priorities.

The last capital plan cost over $32 billion, and the next one is expected to have a pricetag upwards of $50 billion.

Yet with just three weeks until the state-mandated deadline of Oct. 1 for the board’s approval, the list of projects it will fund is shrouded in secrecy.

“There’s a lot in flux right now, with the transformation. I don’t think there’s clear directive or instruction,” said board member Veronica Vanterpool, a Mayor Bill de Blasio appointee, who also has not see the plan.

“There’s just a good deal of confusion as to the process, at least on the part of this board members.”

MTA rep Tim Minton said there will be “some activity” on the capital plan at the board’s Sept. 25 meeting, but that a timeline for its review and approval has not been set.

“There is a process, the process is continuing,” Minton said. “The MTA is committed to being transparent, and seeking input from those who have an interest in the details of the plan.”

The board’s vote is far from the final step.

Once approved, the capital plan will need to earn the unanimous support of the Capital Plan Review Board, whose four members are selected by the governor, mayor and the leadership of each house of the state legislature. That process could take months.

At least one board member is not concerned that the public being will be shut out of the process.

“I have no doubt the capital plan will be made available to the public prior to the board taking action, just as it has always been,” said Sarah Feinberg, an appointee of Gov. Andrew Cuomo.

“I also have no doubt the advocacy community will not be shy about sharing their opinion of the plan, and we all look forward to their comments, press releases, letters and press conferences.”