The city began spending its own money more efficiently by hiring private contractors to take care of some parks, and it also used workfare recipients to clean parks.

Mr. Green said he might be open to letting private companies prune trees or do other tasks, but he expressed doubts about privatization and the use of workfare recipients to clean parks.

Leaders of the group organizing the workfare recipients, WEP Workers Together, say they have a couple hundred members.

Already, Republican lawmakers are considering legislation that would exempt workfare recipients from minimum wage laws.

Union officials said the lawsuit, to be filed in State Supreme Court in Manhattan, would seek an injunction barring workfare recipients from doing jobs once done by city workers.

The rats moved on (to a less organized neighborhood, no doubt), and the city, convinced of the association's argument, arranged to have workfare recipients take over the task of liner replacement.

In contrast, many programs run by nonprofit groups are for workfare recipients who are high school dropouts with few job skills.

Another obstacle is that unions may not be allowed to bargain to raise the wages of workfare recipients because their pay is a welfare check.

One welfare advocate who is trying to unionize workfare recipients said the decision goes a long way toward insuring that workfare workers are treated lke regular workers.

"Our reading of the Fair Labor Standards Act is that it covers workfare recipients," Bruce Reed, the White House domestic policy adviser, said Thursday.