Detroit, the very symbol of American industrial might for most of the 20th century, is drawing up a radical renewal plan that calls for turning large swaths of this now-blighted, rusted-out city back into the fields and farmland that existed before the automobile.

Operating on a scale never before attempted in this country, the city would demolish houses in some of the most desolate sections of Detroit and move residents into stronger neighborhoods. Roughly a quarter of the 139-square-mile city could go from urban to semi-rural.

Near downtown, fruit trees and vegetable farms would replace neighborhoods that are an eerie landscape of empty buildings and vacant lots. Suburban commuters heading into the city center might pass through what looks like the countryside to get there. Surviving neighborhoods in the birthplace of the auto industry would become pockets in expanses of green.

Detroit officials first raised the idea in the 1990s, when blight was spreading. Now, with the recession plunging the city deeper into ruin, a decision on how to move forward is approaching. Mayor Dave Bing, who took office last year, is expected to unveil some details in his state-of-the-city address this month.

“Things that were unthinkable are now becoming thinkable,” said James W. Hughes, dean of the School of Planning and Public Policy at Rutgers University, who is among the urban experts watching the experiment with interest. “There is now a realization that past glories are never going to be recaptured. Some people probably don’t accept that, but that is the reality.”

The meaning of what is afoot is now settling in across the city.

“People are afraid,” said Deborah L. Younger, executive director of a group called Detroit Local Initiatives Support Corporation that is working to revitalize five areas of the city. “When you read that neighborhoods may no longer exist, that sends fear.”

Though the will to downsize has arrived, the way to do it is not clear and fraught with problems.

Politically explosive decisions must be made about which neighborhoods should be bulldozed and which improved. Hundreds of millions of federal dollars will be needed to buy land, raze buildings and relocate residents, since this financially desperate city does not have the means to do it on its own. It isn’t known how many people in the mostly black, blue-collar city might be uprooted, but it could be thousands. Some won’t go willingly.

“I like the way things are right here,” said David Hardin, 60, whose bungalow is one of three occupied homes on a block with dozens of empty lots near what is commonly known as City Airport. He has lived there since 1976, when every home on the street was occupied, and said he enjoys the peace and quiet.

For much of the 20th century, Detroit was an industrial powerhouse, the city that put the nation on wheels. Factory workers lived in neighborhoods of simple single- and two-story homes and walked to work. But then the plants began to close one by one. The riots of 1967 accelerated an exodus of whites to the suburbs, and many middle-class blacks followed.

Now, a city of nearly 2 million in the 1950s has declined to less than half that number. On some blocks, only one or two occupied houses remain, surrounded by trash-strewn lots and vacant, burned-out homes. Scavengers have stripped anything of value from empty buildings. According to one recent estimate, Detroit has 33,500 empty houses and 91,000 vacant residential lots.

Several other declining industrial cities, such as Youngstown, Ohio, have also accepted downsizing. Since 2005, Youngstown has been tearing down a few hundred houses a year. But Detroit’s plans dwarf that effort. The approximately 40 square miles of vacant property in Detroit is larger than the entire city of Youngstown.

Faced with a $300 million budget deficit and a dwindling tax base, Mr. Bing says the city can’t continue to pay for police patrols, fire protection and other services for all areas.

The current plan would demolish about 10,000 houses and empty buildings in three years and pump new investment into stronger neighborhoods. In the neighborhoods that would be cleared, the city would offer to relocate residents or buy them out. The city could use tax foreclosure to claim abandoned property and invoke eminent domain for those who refuse to leave, much as cities now do for freeway projects.