Mayor Michael Bloomberg Tuesday vetoed the most ambitious new oversight proposed in years for the New York Police Department, setting up an override showdown with lawmakers.

Bloomberg's long-expected veto puts the proposals on a course toward what could be a dramatic override vote later this summer.

The measures would create an outside watchdog for the department and a broader path for lawsuits claiming discriminatory policing. The latest in decades-long history of efforts to impose more outside input on the nation's biggest police force, the legislation crystallized from concerns about the NYPD's extensive use of the stop-and-frisk tactic and its widespread surveillance of Muslims.

"[The measures are] dangerous and irresponsible," the mayor wrote in veto messages, saying each "would make New York less safe."

The mayor and Police Commissioner Ray Kelly have argued vehemently that the legislation will undermine safety by deluging the department in lawsuits and inquiries, making officers hesitant to act for fear of coming under scrutiny, and undercutting policing techniques that have cut crime dramatically in recent years.

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Civil rights advocates and other proponents say the measures will make the city safer by repairing frayed trust between police and citizens who feel unfairly targeted by stops and surveillance.

"We can have safety and police accountability at the exact same time," City Councilman Jumaane Williams, who joined Councilman Brad Lander in leading the push for the legislation, said when lawmakers debated the measure.

The City Council passed the legislation last month with enough votes for an override. But the piece concerning discrimination lawsuits passed with just exactly the needed number.

Bloomberg has indicated he'd try to persuade lawmakers to change their minds, and the billionaire mayor has suggested he might amplify his message with campaign contributions: "We'll see what I'm going to do. The bottom line is I make no bones about it: I'm telling you I'm going to support those candidates" who agree, he said this month.

The powerful Patrolmen's Benevolent Association police union has sent thousands of fliers targeting some lawmakers who supported the measures. The mailings tell voters their council members "voted against public safety" and urge constituents to call and complain.