If landlords do not cooperate, the city intends to use eminent domain to take the property, officials said.

The planned acquisition involves 800 apartments spread throughout 25 to 30 buildings, mostly in the Bronx, which has the overwhelming majority of cluster apartments in the city. The city targeted buildings where more than 50 percent of the units were occupied by homeless people — a threshold that would guide future acquisitions, the city said.

In a statement, Mr. de Blasio said his administration had to “think creatively and be bold.”

“We’re fast-tracking the transition from shelter to higher-quality, permanently affordable housing for New Yorkers caught in the grips of our city’s affordability crisis,” he said.

The planned acquisition could place about 3,000 people into permanent housing; in some cases, homeless families living in the apartments would simply stay put, but would no longer be considered homeless. It was not immediately known how much the program would cost the city.

The rise in homelessness has been a paradox for Mr. de Blasio, a self-described progressive railing against income inequality. An estimated 77,000 people were living in the city’s different shelter systems and on the streets in February, according to a count overseen by the Department of Housing and Urban Development. When the mayor took office in January 2014, there were an estimated 68,000.