THE MBTA REVEALED ON MONDAY that it has pared back the cost of the proposed Green Line Extension by $622 million, but Transportation Secretary Stephanie Pollack said it’s still unclear whether the project can or should proceed.

“There are substantial risks that remain,” she said during a briefing for reporters several hours before the state Department of Transportation and the T’s Fiscal Management and Control Board were scheduled to take up the issue.

The Green Line Extension, needed for the state to meet clean air requirements mandated in the wake of the Big Dig, was originally approved with a $2 billion price tag, split equally between the federal government and the T. When problems surfaced with the MBTA’s contracting methods and subsequent cost estimates suggested the price could rise to $3 billion, the T put the project on hold and began trying to figure out a cheaper way to extend the Green Line from Lechmere station into Somerville and Medford.

A report issued on Monday said the T reduced the overall cost $622 million by simplifying the design of the stations, the maintenance facility, and the community path along the route. The report said the cost of the seven stations was reduced by $288 million by reducing the number of elevators and escalators and assuming the development of a cheaper, new fare system that will allow passengers to board by tapping passes at any door. That new fare system allowed the construction of one boarding platform rather than two.

The tab for bridge work was pared back by $35 million, the maintenance facility pricetag was reduced $115 million, and the community path’s cost was cut by nearly $123 million. The new price estimate for the project is just under $2.3 billion, of which the T has already spent $700 million.

With the new price estimate, the T would need to come up with a way to bridge the gap between the earlier $2 billion cost estimate and the new $2.3 billion estimate. The T has pledges of $152 million in repurposed federal highway funds, $50 million from Somerville, and $25 million from Cambridge. That leaves a $73 million shortfall.

But Pollack said the shortfall could rise as the Federal Transit Administration reviews the T’s revised price estimate. She said the T’s estimate is based on very conservative assumptions, but noted the federal agency upped the T’s initial Green Line Extension estimates by $300 million in 2014, and she expects the agency will take a very close look at the new proposal because of the sharp increases in cost estimates that emerged over the last two years.

Pollack said the report released on Monday also highlighted how the T lacks the internal management staff needed to do a project like the Green Line Extension, particularly using a new contracting method called design-build, which would allow the agency to seek bids that could not exceed a certain amount.

The T’s report said a staff of 40 to 50, including a program manager and six deputies, would be needed to build the Green Line Extension. Pollack noted the supply of competent managers for such a project is very limited nationally. “There is no one at the T right now that could manage this project,” she said.

The transportation secretary said she is also worried that the Green Line Extension could distract the T from its core mission, which is to operate the existing T system effectively. “That is my first priority,” she said, noting that the MBTA delivers 1 million passenger trips a day while the Green Line Extension would represent only about 50,000 trips a day, or 5 percent of the total.

Pollack declined to say exactly what she would recommend to the two boards, but insisted the state should not rush the project, as it did the first time around. She said she would wait until after the Federal Transit Administration reviews the T’s new pricing estimates before committing to move forward, even though that delay could trigger cost escalation for the project of $1.6 million a month.