MET Police chiefs have said fewer officers will be on duty during the New Year’s Eve celebrations despite four terror attacks in 2017.
But Supt Nick Aldworth insisted resources used will be “proportionate” and London will be a “safe environment” for revellers.
Scotland Yard said "operational reasons" stopped them from being able to discuss specific numbers on duty this Sunday. There were 3,000 at last year's celebrations.
Mr Aldworth said the public should be "reassured" by the number of officers available.
"I think the message I would give to the public is to be reassured that we've got the right number of officers to police this event," he said.
"We want them (the public) to be alert, not alarmed.
He said there were plans in place should there be a major incident.
About 100,000 ticket-holders are expected to watch the 12-minute fireworks display.
The celebrations come after ISIS threats made on a propaganda poster to unleash "New Year's Eve 'hell'" in the city.
London was hit by four major terrorist incidents in 2017, including March's attack on the Palace of Westminster which saw five people including PC Keith Palmer killed, and June's attack at London Bridge, which left eight people including three terrorists dead.
In May, twenty-three people were killed and hundreds injured when lone wolf Salman Ramadan Abedi detonated a bomb in the foyer of Manchester Arena after an Ariana Grande concert.
Scotland Yard advised people without a ticket for the sold-out fireworks to watch "from the comfort and warmth of your home".
Alongside increased police patrols, mobile undercover units will patrol cities ready to track suspicious targets, while an SAS squadron is on standby in London to back up police if necessary.
In the past, targets London, Birmingham and Manchester have all had undercover units posing as homeless people with sniffer dogs as "pets" to remain undetected.
Meanwhile in Birmingham, armed police have held a night exercise with actors as "victims" to prepare for a possible attack and are said to be stepping up their patrols with an "unprecedented amount of activity", a former intelligence officer told The Mirror.
A spokeswoman for London mayor Sadiq Khan said: "The safety of Londoners is the mayor's number one priority.
"He and his team are in close contact with the Metropolitan Police, TfL and other key agencies, and we have appropriate plans for security in place.”
We pay for your stories! Do you have a story for The Sun Online news team? Email us at email@example.com or call 0207 782 4368 . We pay for videos too. Click here to upload yours.
https://twitter.com/intent/tweet?url=https%3A%2F%2Fwww.thesun.co.uk%2Fnews%2F5234484%2Flondon-police-confirm-nye-celebrations-will-have-fewer-officers-on-patrol-despite-year-of-terror-attacks%2F&text=” target=”_blank” title=”Click to share on Twitter