US police are using a new tactic in the wake of recent terror attacks involving trucks in Nice and Berlin - big trucks in a protective ring.

A cordon of water trucks will be placed around Pasadena's Rose Parade in California. In New York, more than 100 garbage trucks and other vehicles, many filled with sand, will form a protective barrier around Times Square, where well over a million people are expected to gather for a traditional countdown party tonight.

There will be strict controls including personal searches at all entry points, and 7,000 police officers are on standby.

In Pasadena, some 1,500 police officers in uniform as well as civilian clothes will be deployed over the nearly 9km route of the annual New Year's Day parade.

The New York Police Department, Federal Bureau of Investigation and Department of Homeland Security say there is no "specific, credible threat" to the Times Square party, but they "remain concerned about unaffiliated lone offenders and home-grown violent extremists targeting the event".

Performers for the Times Square event include Rachel Platten, Gloria Estefan and Mariah Carey.

"What I want everyone to take away from our preparation is this: People will be safe this New Year's Eve because we are there along with our law enforcement partners," New York Police Commissioner James O'Neill said this week.

"We are going to have one of the most well-policed, best-protected events in one of the safest venues in the entire world."