NYPD Commissioner William Bratton vowed a "safe, happy and memorable" New York City Marathon on Sunday, speaking to reporters Thursday at a Manhattan news conference previewing the event expected to draw more than 50,000 runners and thousands more spectators.

More than 4,000 police officers will be assigned to "primary security" and traffic control at the TCS New York City Marathon, accompanied by four "helicopters," 20 vessels in the city's waterways and counterterrorism and FBI teams, Bratton said.

"So we're very prepared. We're very focused," he said. He added that police are always seeking the public's cooperation and asked them to report suspicious activity.

Bratton stressed that the marathon was to be an enjoyable event for New Yorkers and visitors, touting it as "26 miles without a red light."

NYPD has no intelligence pointing to a specific threat to the marathon, which begins in Staten Island and ends in Manhattan's Central Park, but security will be increased as a precaution, Bratton said at a briefing at the Javits Convention Center with Mayor Bill de Blasio, NYPD Chief of Counterterrorism James Waters and marathon organizers.

Former NYPD Commissioner Ray Kelly "ramped up" marathon security last year in light of the previous year's bomb attack on the Boston Marathon, Bratton said.

"We have kept that same level of security and then some in the event this year," Bratton said. "We're in great shape for this event."

Waters said the NYPD had studied social media feedback to last year's security measures to see if runners felt reassured. Runners will go through magnetometers and must use clear bags to carry their belongings, Waters said.

Marathon stars said they were looking forward to running the race on Sunday.

"You have to perform. You have to persevere," said 2009 marathon winner Meb Keflezighi. "You start together and you finish and everybody feels a great sense of accomplishment."