A South Coast business partnership based at the University of Massachusetts Dartmouth has told the state's transportation secretary it is "open to" exploring an alternative route to bring commuter rail service to the area sooner and at a lower cost than the current planned route.

The SouthCoast Development Partnership, made up of some of the largest employers and institutions in the area, said that in light of new state estimates pointing to increased costs and a lengthier timeframe it is open to learning more about a route that would take the planned South Coast Rail along a commuter rail line that ends at Middleborough, rather than routing it from Stoughton through Easton.

The Stoughton route, which would need to be electrically powered and run through the environmentally sensitive Hockomock Swamp, would cost $3.4 billion with service expected to start by around 2029, the Massachusetts Department of Transportation announced last week. In 2012, the state predicted the project would cost $2.23 billion and start service in 2022.

Former MBTA General Manager Frank DePaola last week said extending service from near the Middleborough/Lakeville terminus would be less expensive and take about six to eight years to complete. The Middleborough route would also add about 15 minutes of travel time to service between Boston and New Bedford and Fall River.

"I'm thankful that the administration is actually taking this up," Hugh Dunn, executive director of the partnership, told the News Service. Anticipating that increased real estate development would follow rail service to the scenic coastal region, Dunn said, "We're watching this happen in Worcester."

"We are very interested in exploring avenues by which rail service could be provided on an expedited timeline - even sooner than the proposed 6-8 year schedule," read the letter signed by the partnership's co-chairs, BayCoast Bank President and CEO Nicholas Crist and Potentia Business Solution Managing Director Dave Slutz. The letter was sent to Transportation Secretary Stephanie Pollack.

The letter referred to the Middleborough alternative as an "interim route." Asked if he would support the Middleborough route even if it wasn't an interim step before service down the Stoughton route, Dunn said, "We'd support it on its own for now."

Rick Kidder, president of the New Bedford Area Chamber of Commerce, told the News Service the Middleborough route "needs to be looked at," so officials can know the length of travel times and sort out capacity issues closer to South Station, which is eyed for expansion and where lines can become congested during peak travel periods.

DePaola said the state could increase capacity on commuter rail routes south of the city by burying tracks beneath a widened Southeast Expressway, which would allow for more trains to serve areas south of Boston during rush hour. No cost estimates were announced for that work.

"The cities of Fall River and New Bedford are the only Gateway cities within 60 to 70 miles of Boston that don't have rail service, to date," Kidder said.

Sen. Marc Pacheco, a Taunton Democrat, said he is skeptical of the updated cost estimates and believes the alternative proposal will divide the region. He prefers the Stoughton route that would include a stop in the heart of Taunton.

"You have the largest-landed city in the Commonwealth of Massachusetts with no core station in the heart of the city - coming through the city - which is included in the Stoughton route," Pacheco told the MBTA's Fiscal and Management Control Board last Monday.

Saying he had been associated with the South Coast Rail idea since the late 1970s, Pacheco said the Stoughton route has "the least amount of opposition."

The partnership's executive board includes representatives of the University of Massachusetts Dartmouth, Bristol Community College, and SouthCoast Health System.