GOV. CHARLIE BAKER on Wednesday defended the MBTA’s pursuit of new commuter rail service to Fall River and New Bedford at a time when the agency is struggling to provide basic core services and its management ranks are stretched dangerously thin.

After outlining what ails the T and his administration’s efforts to turn the authority around, the governor was asked if he was part of the problem by pressing the agency to expand its operations and launch what is known as South Coast Rail.

“I would say the opposite,” Baker said.

In explaining his reasoning, Baker said his administration is trying to fix the T while honoring commitments to expand the Green Line into Somerville and Medford and extend commuter rail to the South Coast. In both cases, the projects ballooned in cost by about $1 billion.

In the case of the Green Line Extension, nicknamed GLX by government officials, the Baker administration responded by redesigning the project and seeking additional funds from host communities to reduce the cost to the original $2 billion pricetag. With South Coast Rail, the administration is exploring an alternative route to Fall River and New Bedford that could possibly reduce the $3.4 billion estimated cost.

“Both the GLX project and the South Coast project are things that fall into what I would call the category of commitments that have been made by the Commonwealth to a lot of different people over a long period of time,” Baker told reporters at a State House press conference.

“It’s a commitment that was made by the Commonwealth,” Baker said of South Coast Rail. “The facts have changed and I think to sort of maintain faith with the people who’ve been faithfully working this one from the other end we have to incorporate that into the way we decide what happens.”

The Green Line Extension was agreed to by the state as part of environmental mitigation efforts negotiated in connection with the Big Dig. South Coast Rail, however, is largely a political commitment made by Baker and most of his gubernatorial predecessors.

“I kind of own a lot of the commitments that were made by the Commonwealth whether I was here or not,” Baker said. “I accept that and believe that’s appropriate.”