England's most senior police officer has urged people to "be calm, be sensible" when pubs reopen on Saturday.
The commissioner of the Met Police, Dame Cressida Dick, said police had been preparing "for some time" and had "extra resources in place".
Greater Manchester Police said it had planned a "significant" operation, while night marshals will be deployed to support officers in Leeds.
Pubs in England have been closed since March to slow the spread of Covid-19.
But Prime Minister Boris Johnson announced last Tuesday that they - as well as bars and restaurants - would be able to reopen on 4 July, with certain restrictions.
Dame Cressida said that she was "not predicting" violence but that there would be "a lot" of officers on the streets, with "more ready... should people get violent".
"My message is, if you're coming out on Saturday, be calm, be sensible," she told BBC Radio 4's Today programme on Tuesday.
"Look after yourself, look after your family. We are still in a global pandemic which is affecting this country very obviously."
Her warning comes after officers were attacked as they tried to break up unlawful gatherings in London last week, with at least 22 officers injured during unrest in Brixton.
Other parts of the UK have announced moves in a bid to ensure a smooth reopening of businesses this week.
Greater Manchester Police has said it has planned a "significant" operation across the region's cities and towns.
Leeds City Council has announced it will provide "night marshals" to help police to "keep things running smoothly".
And police in Suffolk plan to increase enforcement around road safety amid concerns around drink-driving.
Some people have criticised the government's decision to allow pubs to reopen on a Saturday - which some MPs and newspapers have dubbed "Super Saturday" - instead of a quieter midweek day.
Tim Clarke, from the Metropolitan Police Federation, said the weekend could be as busy as policing New Year's Eve.
He added that he feared it could be "anything but a 'Super Saturday' for police officers".
The chairman of West Yorkshire Police Federation, Brian Booth, said he hoped people would "maintain their common sense" as the country continues to live "under the cloud of Covid".
"Prior to the Covid-19 outbreak, local A&Es on Friday and Saturday nights were at times akin to a circus full of drunken clowns. We do not need this once again," he added.
John Apter, the head of the Police Federation which represents rank-and-file officers in England and Wales, told the BBC last week that the government's announcement had created "a countdown to carnival" that could lead to "big problems".
The West Midlands police and crime commissioner, Labour's David Jamieson, has described the decision to reopen pubs in England on Saturday as "pure madness".
Sacha Lord, Greater Manchester's night time economy adviser, said many bars were already "on their knees" but would not be opening on Saturday due a lack of time to prepare.
But Mr Lord said: "It makes more sense to open up on a Wednesday in the middle of the week so staff have got time to get used to this new normal before things get too crowded."
He predicted most drinkers would stay away from the city centre and stay local, while others would "sit back for the next couple of weeks to see how things pan out".
The British Beer and Pub Association, which represents the industry, said it welcomed the move to reopen businesses but called on pub goers to support staff "to ensure everyone can enjoy the return of our pubs safely".
Other parts of the UK have announced later dates for restrictions to be eased.
No date has so far been announced for pubs to reopen in Wales, where ministers say work is "ongoing".