A proposal to extend Oahu’s rail tax has cleared its biggest hurdle yet, with state House and Senate negotiators agreeing to a deal that aims to get the island’s cash-strapped public transit project out of a nearly $1 billion budget hole and finish construction.

Legislative conferees voted unanimously Friday to approve House Bill 134. Ultimately they opted to go with the Senate’s proposal: to extend Oahu’s 0.5 general excise tax surcharge for an additional five years through 2027. The bill would also allow neighbor counties to enact a 0.5 GET surcharge to fund their own transportation-related projects from 2018 through 2027.

Lawmakers removed an 11th-hour bargaining chip that would have required any counties adopting the tax to take ownership of so-called “roads in limbo” — the hundreds of miles of roads across Hawaii whose jurisdiction is disputed by county and state officials.  But they did leave in a provision where the state claims the “air rights” above the rail system.

The state will also retain its 10 percent skim for administering the tax surcharge — a lucrative collection deal that has reaped $163 million for the state so far.

The full House and Senate are expected to vote on the measure sometime next week.