Boston Mayor Martin Walsh had a "very honest, straightforward conversation" Tuesday with Transportation Secretary Stephanie Pollack and MBTA General Manager Steve Poftak, five days after he said he would meet with the officials to discuss investments and improvements at the T.

Walsh told reporters that he met with Pollack, Poftak, his chief of staff Dave Sweeney, Chris Osgood from the city's transportation department and Brian Golden from the planning department Tuesday morning before he came to the State House to testify at a pair of committee hearings.

In the wake of a derailment that has snarled Red Line service and frustrated commuters since June 11, Walsh last week wrote to Pollack slamming the MBTA as "not currently a functional service."

"We need to have a transportation system that works for everyone, and that's ultimately our goal and our plan, and hopefully we'll be able to continue to work and advocate and push, if need be, the MBTA and the systems and the city as well to make it happen," the mayor said Tuesday.

Poftak, who along with Pollack also traveled to the State House after the meeting for a separate committee hearing about transportation capital spending, called his discussion with Walsh "very productive."

"The mayor is concerned, as are we, that the transportation system works for the city and, in particular, that we make progress on the Red Line," Poftak said. "There was general agreement that we would work together with his staff to identify areas where we could improve, and that's something that will be in process for a number of weeks."

In his letter, Walsh asked the MBTA to invest about $9 million to run Red Line and commuter rail trains more frequently as mitigation for ongoing delays stemming from the June 11 derailment. Asked if the T would act on that request, Poftak said internal discussions are still ongoing.

"That's something we're going to work on at the staff level," he said. "I don't have anything more concrete to share with you today."

The T is receiving an unexpected $23 million as part of the state budget approved by the Legislature Monday, an amount that represents that agency's share of a nearly $600 million markup in expected state revenues.

Walsh said he thinks riders will be more willing to tolerate delays if they see T service improving "over the course of the next two months. Gov. Charlie Baker previously suggested more frequent service shutdowns to speed up improvements as he called for $50 million in one-time funding, a request that lawmakers have not taken up.

"I'd much prefer to see delays on the T because of construction than because of derailments," Walsh said.