Alongside the fireworks, sparkling harbour and festivities on New Year's Eve will be a necessary reminder of the threat of terrorism, with authorities preparing to use trucks and bollards to block off Sydney CBD streets to keep revellers safe.

NSW Police Deputy Commissioner Jeff Loy said extra riot squad officers, some with long-arm semiautomatic weapons at their disposal, would be on duty, along with other specialist units, as a million people are expected to come into the city to see in the new year.

Trucks, bollards, and extra police will be used to keep revellers safe on New Year's Eve. Credit:Wolter Peeters

"We're very well aware that the national terrorism threat is 'probable' and we've looked at the issues that happened in Melbourne, and have also occurred around the world," Deputy Commissioner Loy said on Friday.

"We believe that we have a highly visible, and highly responsive police force to any incident at any level."