Boris Johnson has said he will set out a “comprehensive” plan next week on restarting the economy, reopening schools and how people might travel to work, following weeks of lockdown.
The prime minister said the UK was “past the peak” of the coronavirus outbreak and “on the downward slope”.
But he stressed the country must not “risk a second spike” of the virus.
Latest figures show 26,771 people with coronavirus have died in UK hospitals and the wider community, a rise of 674.
The prime minister said that “we can now see the sunlight”, but he insisted that to avoid the “disaster” of a second peak the UK must meet the fifth of five tests before the lockdown can be lifted.
“Nothing we do should lift the R or reproduction rate – back above one,” he said.
More than 81,000 coronavirus tests were carried out on Wednesday, still short of the government’s target of 100,000 by the end of April. Mr Johnson insisted: “We’re massively ramping up testing.”
The reproduction number is a way of rating a disease’s ability to spread and is the average number of people that one infected person will pass the virus on to.
The BBC’s political editor Laura Kuenssberg asked what level the reproduction rate should be before the government would be “comfortable easing restrictions”.
The government’s chief medical officer, Prof Chris Whitty, replied: “We are absolutely confident that the wrong answer is anything over one.”
He explained that as soon as the R rises above one you “restart exponential growth” and “sooner or later” the NHS would be at the risk of being overwhelmed.
Mr Johnson said that keeping the reproduction rate down “is going to be absolutely vital to our recovery”.
Our correspondent also asked whether the economy “just has to wait” as the government continues with the lockdown in the UK.
The prime minister said it was “vital” to avoid a second peak “because that would really do economic damage”.
He added: “That’s why we’ve got to calibrate our measures so carefully and make sure that we not only unlock the economy gradually, but also find ways of continuing to suppress the disease.”
Mr Johnson said face coverings will be “useful” as part of the strategy for coming out of lockdown “both for epidemiological reasons but also giving people confidence they can go back to work”.
Speaking at the No 10 briefing for the first time since recovering from the virus, the prime minister said: “I’m not going to minimise the logistical problems we’ve faced in getting the right protective gear to the right people in the right place, both in the NHS and care homes.
“But what I can tell you is that everyone responsible for tackling these problems – whether in government, the NHS, Public Health England or local authorities – we are throwing everything at it, heart and soul, night and day to get it right, and we will get it right.”
Asked about the UK’s response to the pandemic, Mr Johnson said he thought it was “right to make our period of lockdown coincide… with the peak of the epidemic”.
But he added that the government was “learning lessons every day”.