Differences in a major bill aimed at controlling spiraling health-care costs in Massachusetts are being negotiated in private by the leaders of the House and Senate, bypassing a traditional legislative conference committee and excluding input from Republicans in either chamber.

Instead, Senate President Therese Murray and House Speaker Salvatore DiMasi - both Democrats - are negotiating the bill themselves. They are being assisted by health-care staffers and receiving advice from their two hand-picked chairs of a joint health-care financing committee, Sen. Richard Moore (D-Uxbridge) and Rep. Patricia Walrath (D-Stow).

Although a tight legislative calendar was cited as a reason for not using a broader conference committee to work on the bill, Moore is now in New Orleans, attending a meeting of state lawmakers. Joining him on the trip is Chris Hager, DiMasi’s top health-care aide.

“It’s very unusual for a bill of this importance not to have a conference, or to involve the Republican caucus,” said Sen. Bruce Tarr (R-Gloucester).

In March, Murray proposed a bill that aimed to control costs by developing an electronic record-keeping program, requiring major health plans to publicly disclose the reasons for their annual cost increases, as well as ensuring hospitals and clinics don’t charge for such mistakes as surgery on the wrong body part.

The House approved a similar bill, but with reporting and other technical differences that must be resolved. “The bills are practically identical and everyone felt the small differences could be worked out without going into conference,” said Murray spokesman David Falcone.

David Guarino, DiMasi’s spokesman, said the differences were being dealt with by the office staffs, as well as Moore and Walrath.

“We are obviously hopeful not to need a conference committee given the limited number of days left of formal sessions,” said Guarino. “If a conference committee proves necessary, we will certainly appoint one.”