The Big Apple is a popular destination on December 31, with about one million people packing into Times Square every year for the countdown to midnight and the traditional ball drop.

"I certainly understand that everyone's concerned and I want everyone to understand and to hear that the NYPD is ready," De Blasio said in a local radio interview.

"The planning is extraordinary. We'll have a huge number of police out on New Year's Eve, including a lot of our new anti-terror force, the Critical Response Command. That's 500-plus officers ... who are specialized in preventing terror."

A total of about 6,000 officers will be on hand, the city's police chief Bill Bratton told reporters, noting that some would be in plain clothes.

After the Paris attacks on November 13, an Islamic State group propaganda video broadcast images of New York from Times Square.