DENVER, Colo. — A compromise plan to fix the rusting Capitol dome with a mix of public and private money advanced Tuesday in the Senate, but the lawmaker behind a competing proposal in the House said he didn't like the deal.

The stalemate is the latest twist in the saga behind fixing the cylindrical drum of the dome, a 19th-century structure made almost entirely of cast iron and now rusting so badly that workers in 2007 closed off a walkway to the public after a 10-pound chunk of metal fell down.

State architects estimate it will take $11.6 million to repair the cast-iron sections, a process that could require patching holes and possibly recasting some sections.

Sen. Mike Kopp, R-Littleton, on Tuesday rolled out a compromise bill that would take $4 million from the State Historical Fund in the first year, then rely on private fundraising in years two and three. Anything less than $4 million in private funds raised in those last two years would be backfilled by historical-fund money. The fund now is used to provide historic preservation grants to buildings across the state.

"We've got to get this (dome) fixed," Kopp said. "This is an opportunity for us to get the two bills webbed. You guarantee that we come up with a $12 million funding stream."

The Senate gave the bill initial approval and must vote on it once more before it can move to the House.

Kopp originally wanted to use nearly $12 million over three years from the State Historical Fund to help pay for repairs.

Rep. Jim Riesberg, D-Greeley, favors private funding, arguing that it would be wrong for lawmakers to use $12 million from the historical fund, which is financed by a portion of casino tax revenues.

Riesberg's bill would allow the state to seek a historic preservation grant for the dome. He said there are safeguards in the legislation to make sure corporate donors don't slap their logos on the scaffolding as the structure undergoes repairs.

Several Senate Democrats who had favored Riesberg's approach said they liked Kopp's revised proposal.

"This is really the best of both worlds," said Sen. Paula Sandoval, D-Denver. "It ensures us that our dome will be addressed and that further deterioration will stop."

The State Historical Society, which administers the historical fund, is taking a neutral position on Kopp's proposal, but Colorado Preservation Inc., which helps carry out many of the hundreds of preservation projects aided by grants from the fund each year, opposes the plan.

"We still feel we've got the ability to raise the money privately for the dome and get it all done at once," said Jim Hare, executive director of Colorado Preservation Inc.

Riesberg said he was not backing down. He said he thinks it's wrong to require that historical funds be used for the dome instead of going through the normal grant application process like other preservation projects.

"I would not be on board with that (Kopp's proposal) because it's taking money instead of asking for it," he said. "My bill asks for it."

Riesberg's measure, House Bill 1402, has passed the House and was scheduled for a hearing before the Senate Finance Committee late Tuesday.

Gov. Bill Ritter's office has said it favors a hybrid of the two bills, but Riesberg said he's not changing his.

"Only one of these bills will be signed," he said.

Kopp said that could mean that the House kills his bill and the Senate kills Riesberg's — which would leave the issue unaddressed.

"That intractable attitude is not going to help get the dome fixed," Kopp said.