Boris Johnson has admitted he's less optimistic that all Covid restrictions will be lifted on June 21.
In what is perhaps his biggest signal yet that the roadmap will be delayed, the PM said he was prepared to be "cautious" over entering the fourth stage.
There have been reports this week that the final easing of restrictions could be delayed by a month, in order to vaccinate more people.
Currently Covid cases are rising rapidly across the country, in part due to the emergence of the more infectious Delta strain.
Locally, in the North East, cases are also increasing quickly. Last week, in Northumberland, they more than quadrupled.
And while the vaccines have dramatically cut the number of deaths, the PM accepted more people are now being admitted to hospital again, leaving him with a huge decision to make before he is expected to address the nation over any changes on Monday.
And addressing the concerns about the mutant strain, he told Sky News: "We don't know to what extent that exactly is going to feed through into extra mortality but, clearly it's a matter of serious, serious concern."
And he accepted that it was "certainly fair" to say he was less optimistic about 'Freedom Day' taking place on June 21 than he was even just a few weeks ago.
However, he has confirmed that scientists are in agreement that restrictions should not currently be rolled back - meaning a return to tougher rules and even further lockdowns to combat the rising cases are off the cards for now.
"The context has radically changed because of the sheer number of people who have been vaccinated and particularly the elderly and vulnerable," he added.
"So the objective now is to give that vaccination programme the legs, the impetus, the speed it needs to beat the spread of the virus. And I've got no doubt that we can."