BOSTON — House and Senate negotiators are once again trying to resolve differences over proposals to revamp the state’s voter-approved recreational marijuana law.

Friday’s meeting of a six-member conference committee came two weeks after an original deadline set by legislative leaders to reach agreement on a final bill. Lawmakers have apparently been struggling to find common ground on issues including taxes, regulatory oversight and local control.

Democratic Rep. Mark Cusack said before Friday’s closed-door session he was optimistic a deal could be struck, but offered no timetable.

A House-passed bill overhauling the law would raise the marijuana tax to 28 percent and give local officials more control over pot shops within their communities. The Senate approved a more modest version on the bill that keeps the tax at the current 12 percent.