HONOLULU — A bill to fund Honolulu’s financially troubled public rail transportation project advanced Tuesday in the state Senate and is heading for a final vote by the legislative body.

Senators voted 17-7 to keep the bill alive with little discussion. However, the vote could be closer during the Senate’s third and final reading Wednesday.

The $9.5 billion rail transit project that would create a commuter rail system for the Honolulu area is underfunded by as much as $3 billion. Lawmakers are considering raising the state hotel tax and extending a surcharge on the general excise tax to close the gap.

State Sen. Laura Thielen, who voted against advancing the bill, said there is traditionally more debate when bills are up for final reading.

Before the Tuesday vote she mentioned on the Senate floor a 2006 news article that estimated a $3 billion total price tag for a proposed rail line that would have gone as far as the University of Hawaii — farther than the current proposed route.

“When people say that the rail cost has gone up — you know, it’s doubled — it’s actually more than doubled because we’re not doing the last two miles from Ala Moana to Manoa, and that would be a really expensive portion of rail,” Thielen said in an interview. “So the price is going up and we’re getting a shorter rail, and really it’s that last segment that would have given you the most traffic relief, because traffic is way worse when UH is in session.”

The vote followed an hours-long Senate committee hearing Monday night when the bill survived by just one vote.

If the bill passes the Senate on Wednesday it will go next to the House for committee hearings and a vote.

Rail officials must present an adequate funding plan to the U.S. government by Sept. 15 or risk having to return more than $800 million already spent of a total $1.5 billion in promised federal dollars.