Video report by ITV News Political Correspondent Paul Brand
Boris Johnson has said the Covid situation in Greater Manchester is "grave and worsens each day" and stressed he will intervene if an agreement is not reached on Tier 3 restrictions.
Speaking at a government briefing on the coronavirus pandemic, the prime minister said the government has not yet reached an agreement with Greater Manchester leaders and Mayor Andy Burnham.
Mr Johnson said Covid cases in the region have doubled in the past few days and high infection rates have been creeping up the age range.
Twice during the briefing the PM pointed to the power of "the national government" to "step in and do what is necessary" with regards to the row over restrictions in Greater Manchester.
He warned: "without action there is no doubt that our NHS would be struggling."
"In two weeks, there will be more patients in ICU than at the peak of the first wave," Mr Johnson said.
Responding to Mr Johnson's claims the leaders of Greater Manchester issued a statement saying they had been told there would be another meeting to reach an agreement on Friday, but they were never contacted.
They said: "We can also say with confidence that we have done, and will continue to do, everything within our power to protect the health of our residents."
Mr Burnham and council leaders across Greater Manchester responded by insisting they have done “everything within our power to protect the health of our residents”, and said people and firms need greater financial support before accepting a Tier 3 lockdown.
“At our last meeting with Downing Street officials yesterday morning, we were told they would arrange a further meeting later in the day to provide a response to our requests,” they said in a statement.
“That did not happen and, despite being on standby all day today, we are still waiting for it to be arranged. We can assure the Prime Minister that we are ready to meet at any time to try to agree a way forward.
“We do not believe that the current proposals provide adequate support and that is why we await further talks.”
ITV News Correspondent Stacey Foster discusses Greater Manchester's response
They said they were not convinced a Tier 3 lockdown was the right option to control the virus.
They suggested reintroducing shielding and quicker penalties for businesses that did not conform to current guidelines.
In his opening comments at the briefing, the PM thanked the leaders of other local areas where agreements have been reached.
Paul Brand on what the Prime Minister's options are
"In particular I would like to thanks Steve Rotheram in Merseyside, Sadiq Khan in London, and local leaders in Lancashire who have worked constructively with us," the PM said.
He continued: "Now, we have not yet reached an agreement with Greater Manchester. I completely understand the reluctance of the Mayor and his colleagues to take Manchester into the higher level alert level".
Mr Johnson called on Mr Burnham and other local leaders to "reconsider and engage constructively" on the measures.
His comments come after foreign secretary Dominic Raab warned earlier in the day that the government has the power to impose tougher measures amid a row with local leaders.
Pressed on calls for another national lockdown across the country, the PM said he wanted to avoid it "if at all possible" but added he "cannot rule anything out".
The row over the Tier system in Greater Manchester has intensified over the course of the week with Labour Major for the area Andy Burnham telling Number 10 the city will "stand firm" against being placed under the 'very high' Covid alert level.
It comes after the government announced that a further 1.5 million people in England will be placed under the toughest coronavirus restrictions as Lancashire moves into Tier 3.
When asked about why the government hasn't applied "draconian measures" in the style of a nationwide lockdown, Mr Johnson said his "judgement" had been to pursue local restrictions.
Calls for a "circuit break" lockdown have also dogged the government this week, after Number 10 was accused of "ignoring its own scientists' calls for an immediate two or three week national lockdown."
Labour leader Sir Keir Starmer also pushed for such a measure, putting Mr Johnson under pressure on the issue in Prime Minister's Questions.
But standing alongside the PM at Friday's briefing, chief scientific advisor Sir Patrick Vallance stressed "other harms" of national lockdowns need to be considered.
Sir Patrick acknowledged scientists had advised the government of the need for a national Covid circuit-breaker lockdown in September.
The chief scientific advisor admitted "baseline" Tier 3 restrictions on their own would not be enough to get the numbers of Covid infections down.
He stressed, however, that "there are a number of ways that it can be done" including "higher levels in Tier 3" measures.
Watch the government Covid briefing in full:
Sir Patrick outlined the latest data from the Covid second wave, stressing the R number (rate of reproduction of coronavirus) has risen.
He added, however, that it has not gone up to a rate of three, due to the restrictions which are in place.
Covid tiers: What are the differences between each alert level?
Medium (Tier 1) - Rule of six applies indoors and outdoors. Pubs and restaurants close at 10pm.
High (Tier 2) - Households must not mix indoors in any setting including pubs and restaurants. Rule of six applies outdoors
Very high (Tier 3) - Households must not mix indoors, or in private gardens. Rule of six applies in outdoor spaces including parks. Pubs and bars which don't serve meals will be closed
Sir Patrick warned that Covid infections have been increasing in people over 60 - particularly in the North West and North East.
He confirmed the infections have been spreading from younger to older people, leading to increased hospital admissions.
He warned: "We are not where we need to be and there is more work to be done to get where we need to be."
On an update to the country's Covid testing capabilities, Mr Johnson said the UK has "started building the domestic infrastructure" to provide more rapid saliva tests which could provide results in just 15 minutes.
The tests are already being used in hospitals, but Mr Johnson said the government plans to "start distributing and trialling tests across the country".
Mr Johnson said: "Over the next few weeks we will start distributing and trialling these tests across the country. This will enable us to do quick turnaround tests on NHS staff and care home staff more frequently.
"By testing more frequently and quickly than ever before we can help the spread of the virus spreading through care homes."
He added: "We will be able to test students in universities with outbreaks as well as children in schools, helping us to keep education open safely over the winter."