Leaders of New York's 18,500-member police union reported tentative agreetment on a new contract yesterday. New Orleans garbagemen were told to end a wildcat walkout and get to work. Hundreds of Philadelphia's striking Employes, under a work-or-get-fired order, were back on the job.

New York Mayor Edward Koch branded as "thugs" scores of police officers who impeded delivery of The Daily News Tuesday, and warned that picketing off-duty cops who violated the law would be arrested, suspended and prosecuted.

Hours after Koch's warning and a concession by the city on two major contract issues, the Patrolmen's Benevolent Association tentatively agreed to a two-year contract and said its 355-member delegate assembly will meet on it this morning.

Off-duty police, demonstrating outside the newspaper in protest against editorials unfavorable to their contract position, were hit with water bags thrown from windows and responded by stopping delivery trucks.

The union called a halt to demonstrations after the accord was reached.

The two-year pact provides annual 4 percent wage increase plus cost-of-living adjustments, raising the average patrolman's salary to about $19,100 from $17,540.

New Orleans Mayor Ernest Morial angered by a two-day wildcat walkout by garbagemen, warned them to be on the job this morning or face disciplinary measures.

The 300 garbagemen stopped worked Tuesday in a dispute over equipment breakdowns. About 60 returned to work before dawn yesterday but were chased off by strikers.

Hundreds of Philadelphia prison guards, some court employes, members of the city youth detention center staff and sheriff's deputies took Mayor Frank L. Rizzo's back-to-work ultimatum at face value and returned to work yesterday. But most of the 20,000 remained on strike.