NEW YORK, United States (AFP) — Manhattan, where the scent of marijuana laces the air from housing projects to swanky Soho, will stop prosecuting thousands of people for pot possession and smoking, even if you still risk a US$100 fine.

The new policy will be rolled out from August 1 and could see marijuana prosecutions fall 96 per cent from around 5,000 to 200 a year in Manhattan, the office of district attorney Cyrus Vance announced Tuesday.

It is part of a wider effort by Mayor Bill de Blasio and the New York police department to review how law enforcement deals with low-level marijuana crime. Recreational use of the drug remains illegal in the city.

Blacks and Hispanics are arrested for marijuana at much higher rates than those in predominantly white communities. Arrests can negatively impact job opportunities, schooling and immigration status.

Four years ago, Brooklyn, the most populous of New York’s five boroughs, announced it would no longer prosecute the vast majority of people arrested for pot possession.

Vance said the aim was “a safer New York and a more equal justice system.”

“The ongoing arrest and criminal prosecution of predominantly black and brown New Yorkers for smoking marijuana serves neither of these goals,” he said.

Discussions were ongoing to consider “limited exceptions” to the policy.

Brooklyn’s late district attorney announced a similar policy in July 2014, saying law enforcement resources could be better used elsewhere and that petty offenders should not be saddled with a criminal record for a minor offence.

Low-level marijuana cases are better dealt with summonses than arrests, his successor, Eric Gonzalez, said Thursday.

Possession of up to 25 grams (less than an ounce) of marijuana is punishable by a US$100 fine on first offence in New York, rising to US$200 second time around.

Three months ago, Brooklyn began a pilot program declining to prosecute some instances of smoking marijuana in public.

New York is one of 29 US states to have legalised marijuana for medical use to help patients with cancer, HIV, Parkinson’s, epilepsy and other conditions.