By Laila Kearney

NEW YORK (Reuters) - New York City police officers are voting this week on whether to extend the 16-year reign of Patrick Lynch as their union leader or heed critics who have said his confrontational style is out of sync with the prevailing climate in the largest U.S. city.

Lynch, 51, who has run unopposed for more than a decade, is facing two challengers this year for the presidency of the Patrolmen's Benevolent Association, the city's largest police union, representing nearly 23,000 officers.

Ballots were mailed on May 21, and the deadline for union members to return them is Friday morning. The PBA expects to announce the winner by later in the day.

Lynch was elected union president in 1999 and became known for challenging Michael Bloomberg and Rudy Giuliani, Mayor Bill de Blasio's predecessors, over issues like police benefits and safety.

The challengers, Brian Fusco and Ronald Wilson, have said Lynch's trademark combativeness has begun to work against the interests of the police force. Fusco and Wilson have 27 and 28 years on the force, respectively.

Neither Fusco nor Wilson could immediately be reached for comment. Lynch's representatives did not respond to a request of comment.

Lynch attracted attention last year for engaging in a months-long public battle with de Blasio as tensions rose between the NYPD and the public. Civil rights activists in New York City and elsewhere in the United States have decried police treat of African-Americans and other minority groups.

Lynch accused de Blasio of being too sympathetic toward demonstrators who took to the streets after a number of high- profile incidents involving police and black men. At the same time, he said the mayor was overly critical of police officers charged with enforcing the law.

Tensions between Lynch and de Blasio came to a head in December after two uniformed New York City police officers were shot dead by a man who said on social media that he wanted to avenge the deaths of men killed in confrontations with police.

Lynch reviled de Blasio, saying he had "blood on the hands" and blaming him for anti-cop sentiment in the city. Police turned their backs on the mayor at the officers' funerals.

Lynch's opponents have said his public remarks exacerbated tensions with the mayor and public.

Lynch and de Blasio appear to have settled their differences, shaking hands at a funeral last month for an officer who was shot and killed while on patrol.

Still, another point of contention emerging between them is the number of police on the NYPD. In his preliminary budget proposal, de Blasio excluded funds for hiring hundreds more officers, bucking the wishes of his own police commissioner William Bratton and police unions.

Lynch said on the PBA website that a shortage of patrol officers has led to an increase in murders and shootings in the city this year. He and his challengers agree on this, but Fusco and Wilson have faulted Lynch for failing to negotiate a contract for officers to replace the one that expired in 2010.

Lynch has said he is confident he will get a fair deal on pay and benefits for members and points to cumulative raises of 56 percent he has secured for them during his tenure.

(Reporting by Laila Kearney; Editing by Toni Reinhold)