British Prime Minister Boris Johnson threatened Friday to impose new coronavirus restrictions on Manchester after a stand-off with the city's leaders risked undermining his strategy to drive down infections.

Johnson imposed further restrictions on about 1.5 million people in nearby Lancashire on Friday in a bid to bring down spiralling transmission rates in northwest England.

But Manchester mayor Andy Burnham is fighting against plans for his city to also be moved into "Tier 3" -- the highest level of regional lockdown under Johnson's localised strategy -- without extra funding from central government.

The stand-off comes as different parts of the UK become increasingly subject to varying degrees of restrictions, particularly in devolved Scotland, Wales and Northern Ireland. 

Johnson admitted he had "not yet reached agreement with Greater Manchester", adding he understood the reluctance for deeper lockdown, calling it "far from a pain-free course of action".

"But I must stress the situation in Greater Manchester is grave and it worsens with each passing day," he said at his weekly coronavirus briefing. 

"If agreement cannot be reached, I will need to intervene in order to protect Manchester's hospitals and save the lives of Manchester's residents," he added.

Burnham on Thursday accused Johnson of "asking us to gamble our residents' jobs, homes and businesses and a large chunk of our economy on a strategy that their own experts tell them might not work".

Unrelenting rise 

Foreign Secretary Dominic Raab responded on Friday, saying that the Labour mayor was "effectively trying to hold the government over a barrel over money and politics".

Pubs and bars across Lancashire will now be forced to close unless they serve alcohol as part of a sit-down meal from Saturday.

People are also banned from mixing with others in any indoor setting or private garden.

Casinos, betting shops and soft-play areas will all shut, although gyms can remain open under the new rules, which will be reviewed every two weeks.

Health Secretary Matt Hancock warned of "an unrelenting rise in cases in Lancashire".

"I know how heavy these additional challenges will weigh on everyday life for the people of Lancashire but they are critical in bringing this virus under control," he said.

"Without them, we risk the health of your loved ones, your most vulnerable, and your local NHS services. Now is the time to play your part, and we will make sure you are supported."

Lancashire County Council leader Geoff Driver said he had agreed "a bespoke deal for Lancashire that means our businesses and residents will receive extra support that will not be available elsewhere in the country".

Britain has been the hardest hit country in Europe, with over 43,000 deaths of those testing positive for the virus.

The Scientific Advisory Group for Emergencies (Sage) said Friday that the reproduction number for Britain had ticked up slightly to between 1.3 and 1.5, up from 1.2 to 1.5 last week.