Austin City Council members took a wait-and-see stance Thursday on the expanded downtown rail plan that city staff unveiled this week.

They'll wait for specific answers about the costs and how to pay for what would be light rail or streetcar lines throughout downtown, then consider putting rail bonds before voters. But they emphasized that such a bond package would also have road, bicycle and pedestrian projects.

The city Transportation Department will present more details on the rail plan, including costs, in late April and a financial plan April 29. The council is tentatively scheduled to vote May 27 on its preferred route and how to pay for it.

By law, the council may call an election no later than 70 days before Election Day, the city clerk's office said Thursday, meaning that the council would have to decide by its Aug. 19 regular meeting whether to put transportation bonds on the Nov. 2 ballot.

We either have good answers, or we don't at that point, Mayor Lee Leffingwell said. If we don't have those answers, we won't go ahead. We're not going to put forth a proposal that's not fully cooked.

The urban rail plan released Wednesday was more extensive than a single-route plan that had been on the table for several years. Instead, the plan shows two north-south routes through downtown connected by two east-west lines.

The rail line would run from the Mueller redevelopment in East Austin, pass by the University of Texas and the Capitol complex, then feed into a rectangular route running along 17th and 18th streets on the north, San Jacinto Boulevard and Congress Avenue on the east, Fourth Street on the south, and Lavaca and Guadalupe streets on the west.

It would continue across Lady Bird Lake to Riverside Drive and then to Austin-Bergstrom International Airport, but for now, city staff has not recommended an exact spot for crossing the river.

Council Member Mike Martinez said the project, which earlier had been estimated at about $625 million in 2008 dollars for a single line, would probably exceed $1 billion , taking into account the expanded plan and that construction of the various pieces would be built in phases over several years.

Obviously, we don't have the bonding capacity to build the whole system with local funds, Martinez said.

City staff envisions an initial downtown segment paid for with local or state money, with the outlying pieces primarily financed with federal transit grants.

Council Member Bill Spelman said Thursday that he and others on the council are putting together a list of questions they want answered before calling an election. Spelman has previously said he is doubtful such a plan would be ready to put on the November ballot.

Leffingwell, sensitive to criticism that money spent on rail might cut into the city's ability to pay for other services it provides, said emphatically that neither the initial costs to build the line, nor the annual operating costs, would come from the city's general fund.

No one is saying at this point, however, what those alternative sources of money might be.