State lawmakers continue to carve out a plan that would extend Oahu’s rail tax, as project supporters and opponents fiercely debate the best direction for rail at the state Capitol.

On Tuesday, the Senate Ways and Means Committee voted 8-2 to advance House Bill 134, which would extend the rail tax by five years, through 2027. It would also limit those tax dollars to building the project; the money wouldn’t be used for operations.

Rail officials, led by Hono­lulu Mayor Kirk Caldwell, again pressed for lawmakers to instead pass a 25-year tax extension that would allow crews to keep building the system to Kapolei and the University of Hawaii at Manoa campus — as the public originally envisioned. Caldwell suggested that lawmakers could revisit the project five years after passing an extension to decide whether to proceed with the tax. It would allow the Legislature "to hold our feet to the fire," he said.

However, committee chairwoman Sen. Jill Tokuda pressed back. She said that any tax extension passed this year should go toward only getting rail past its current fiscal crisis and finishing the original 20-mile system.

"The Senate is just trying to help you finish what you started," Tokuda (D, Kailua-Kaneohe) told Caldwell during a Ways and Means meeting Tuesday. The project currently faces as much as a $910 million budget gap.

Limiting the tax surcharge dollars to capital improvements would make sure rail officials don’t use those funds for operations — and Tokuda said she hoped the move would also encourage the city to come up with a detailed, sustainable plan to cover those operations costs.

"We don’t want to give the city a crutch, and a false crutch at that," Tokuda said after the meeting.

Sen. Sam Slom, the chamber’s lone Republican and a staunch, longtime opponent of the rail project, voted against the bill, along with Sen. Gil Riviere (D, Heeia-Laie-Waialua), who has argued against passing an extension this session.

The bill now goes back to the House, and ultimately Gov. David Ige will decide whether to sign the extension into law. On Tuesday, he reaffirmed his view that it’s premature to consider an extension of the 0.5 percent Oahu general excise tax surcharge that’s funding most of the project.

"The fundamental questions that I will be asking depending on where the Legislature ends up is really, is it necessary at this point in time? Has the HART management really taken all the action required to get a better handle on management of the costs?" Ige said Tuesday at a press conference in his offices.

Meanwhile, Honolulu Authority for Rapid Transportation officials this week released a new letter from top Federal Transit Administration officials. It supports the notion that the city has little wiggle room — if any — to change the project so it’s less expensive without breaching their federal agreements and having to pay back the $360 million in federal dollars spent so far on rail.

"Should Honolulu … elect to change the (rail) technology now, however, the current project would come to an immediate end, the FTA would seek repayment of the federal funds provided to the project thus far," FTA acting Administrator Therese McMillan told HART Executive Director Dan Grabauskas in the Friday letter.

McMillan further said that if HART couldn’t complete rail, "repayment of the federal funds would be required."