The prime minister is “determined” that the remaining coronavirus restrictions in England will be lifted on 19 July.
Boris Johnson confirmed that measures would remain in place until then because of the rapid spread of the Delta variant.
That would be the “terminus date” for the remaining restrictions on social contact, he said.
However some Conservative MPs are concerned they could remain for longer.
Scientists advising the government had warned of a “significant resurgence” in people needing hospital treatment for Covid-19 if stage four of easing the lockdown went ahead as planned on 21 June.
The prime minister said a four-week delay would allow more people to get vaccinated.
However, a few restrictions are being lifted on 21 June, including the limit on wedding guest numbers – although venues will still have to adhere to social distancing rules.
Addressing MPs, Health Secretary Matt Hancock said the decision had been made with a “heavy heart” but the race between the vaccines and the virus “isn’t over yet”.
