Seattle City Councilman Peter Steinbrueck poured more cold water Wednesday on King County Executive Ron Sims' proposal to build a 1.1 million-square-foot office tower across the street from City Hall.

Steinbrueck, chairman of the City Council's Urban Development & Planning Committee, said the county would have to make a compelling case for rezoning to allow a building of up to 44 stories in the spot now occupied by the nine-story county Administration Building.

Because the county wants a rezone to put together a more financially attractive project, Steinbrueck said, "I sort of look at that as an abuse of the code, frankly. It's not our job to provide subsidies through code exceptions, which is what this is about." His comments came a day after Deputy Mayor Tim Ceis said Mayor Greg Nickels wouldn't recommend the City Council rezone the block just south of City Hall to allow a building taller than new rules allow. That's where Sims wants to raze the 35-year-old county building in favor of a larger building that would be a joint public-private project.

If approved by the city, the new building would be one of the largest downtown. It would be smaller than the Columbia Center but about the same size as the Washington Mutual Tower, Two Union Square and Seattle Municipal Tower. Sims said Wednesday the Administration Building — which he called an "eyesore" — will be replaced only if it can be done without using tax dollars. The county is asking developers to submit ideas for a building that would include county offices, as well as private offices, shops, apartments or condos.

Total project costs are estimated at $450 million.

Mike Hassenger, a principal in The Seneca Group, which is advising county officials on the project, said it appears a new building could be developed without cost to the county but only if zoning is changed to allow the larger building. Hassenger said the project apparently could fund a tunnel to replace the skybridge that connects the Administration Building to the courthouse and jail.

It is believed the project also could pay for restoration of the King County Courthouse's once-grand south entrance, which has been turned into a loading dock, Hassenger said.

Sims suggested that Seattle "swap" the unlimited-height zoning at the site of the county jail with the 340-foot limit of the adjacent Administration Building block.

The idea didn't impress Steinbrueck, who said, "We can't simply swap one block out for another and preserve the integrity of that plan. It doesn't work that way. We have to look at the bigger picture here."

Seattle Times researcher Gene Balk contributed to this report.

Keith Ervin: 206-464-2105