Honolulu's plan for a $5 billion mass-transit system has hit a speed bump, and a key decision over what type of vehicles to ride remains up in the air.

Mayor Mufi Hannemann's controversial plan to have a five-member panel of experts choose the vehicle technology has been delayed by at least one month, and City Council support for the plan remains shaky.

A final council vote on creating the panel had been scheduled for today, but Chairwoman Barbara Marshall said she pulled the item off the agenda because Hannemann's administration had not provided enough information about the experts under consideration.

The vote is expected to be very close in the sharply divided council and could hinge on Marshall's support. She said she was open to creating the panel but did not want the process rushed through.

The administration had courted Councilman Romy Cachola to become the swing vote, but he said in a letter to Hannemann last week that he had "grave concerns" about handing such a decision over to outside experts.

Cachola said he worried that would "cast a negative image on the council and this project, which will be our city's most expensive endeavor to date."

Council backers contend that creating the panel would insulate the vehicle decision from lobbying and political influence, as companies maneuver for lucrative deals to supply various kinds of trains and technologies.

But opponents maintain that the arrangement would shirk the council's duty and shield the decision from voter accountability, while creating more opportunities for manipulation by special interests.

Hannemann said he wanted "an open, transparent process" and did not consider the delay significant.

"If the council wants more time, that's OK," he said. "As long as we're moving forward."

But Hannemann said he was disappointed by Cachola's stance, especially since council support of the transit route along Salt Lake Boulevard brokered by Cachola is also shaky.

"It would be utterly foolish for Romy Cachola to not support the panel," Hannemann said. "He better think long and hard about that position."

The administration last week released a list of 16 people who could serve on the panel. Marshall said she wants to know specifically who Hannemann would choose, and needs more details about their transit experience.

A council committee last month tentatively approved a plan that calls for Hannemann to appoint two experts who have no links to companies that could bid on the project. Marshall and council Transportation Chairman Nestor Garcia would each appoint one more member, and those four would choose the fifth.

Hannemann has long favored an elevated rail-transit system on steel tracks. Other options include a monorail on rubber tires or a train that glides on a cushion of magnetic levitation.

Some council members and others are pushing for a buslike system that Hannemann says would not meet criteria included in key planning documents that qualify the project for crucial federal grants.

The council agreed last year to plan a "fixed guideway" system that calls for some form of train, and rejected a "managed lane" alternative that could accommodate buses.

A firm decision on the type of vehicle must be made before an environmental impact statement for the project can be completed and allow construction to begin. Hannemann hopes to break ground by 2009.

The 34-mile system is to run from Kapolei to Ala Moana, with spurs to Waikiki and Manoa.

Reach Johnny Brannon at jbrannon@honoluluadvertiser.com.