0601 GMT November 15, 2019
The Federal Bureau of Investigation (FBI) is boosting the number of agents and staff in some of its 24-hour command centers around the country, including New York, Los Angeles and Washington, DC.
The New York Police Department (NYPD) says it will deploy 6,000 police near Times Square, the biggest such deployment ever.
An estimated 1 million people are expected to attend the New Year's celebrations in Times Square.
"On New Year's Eve, the department will be out in force," Mayor Bill de Blasio said Tuesday. "There will be a tremendous number of officers you will see and many you won't see."
The Los Angeles Police Department (LAPD) will deploy extra officers in downtown, where thousands of people are expected to partake in New Year celebrations.
Another top security concern in Los Angeles will be during the Rose Bowl game, an annual American football match played by US colleges which draws a significant number of residents and tourists in the region.
US President Barack Obama has been briefed by his top security officials on security threats facing the nation over the year-end holidays, according to senior US officials briefed on the matter.
Among the threats Obama was told of was one originating abroad, warning of possible attacks in three major US cities, New York, Los Angeles and Washington, DC.
High-profile attacks claimed by the Daesh (ISIL) terrorist group in 2015 has cast a shadow over public gatherings in cities across the globe.