Cabinet Office minister Michael Gove was unable to say how long the new coronavirus measures across England are expected to last.
From Thursday evening, all pubs, bars, restaurants and other venues in England will be required to close by 10pm.
The 10pm curfew, used elsewhere in local lockdowns, will be rolled out across the country to try to prevent alcohol-fuelled breaches of social distancing rules.
Further steps will be announced by Prime Minister Boris Johnson when he addresses MPs later on Tuesday, Mr Gove says.
“What we hope is we can take appropriate steps now, which mean that if we succeed in beating back the virus, then we will in the future be able to progressively relax them,” he told BBC Breakfast.
“But what I can’t do is predict with absolute certainty.”
Pressed on whether it would be months or weeks, Mr Gove said: “It is the case, as Professor Vallance and Chris Whitty pointed out yesterday, that we’re going to have a challenging next six months.”
When asked about evidence around the 10pm hospitality curfew, Mr Gove told BBC Breakfast: “There is evidence that the longer venues stay open, the greater degree of social mixing that takes place.
“So, placing a restriction like this is something that we’ve already done in parts of the country where the virus has been spreading particularly fast.”
He added: “I think it will make a difference, but I think that there are other steps that require to be taken as well, and the Prime Minister will be saying more to the House of Commons.”
It comes after he said people should now work from home if they can, in efforts to “restrain” social mixing as much as possible.
“If people can work from home, they should,” he told BBC Breakfast.
“But I stress that it’s very important that those people whose jobs require them to be in a specific workplace do so.”
He added that it was not a case of “revisiting the days at the beginning of our response to this virus” as “workplaces are safer”, adding: “But one of the risks that we have to face is that social mixing overall contributes to the spread of the virus.
“So as much as we can restrain that as possible at this stage, the better for all of us and for public health.”
Wales’ health minister Vaughan Gething welcomed Cabinet Office minister Michael Gove’s comments about people working from home.
“The Welsh Government has continued to advise people to work from home if you can,” Mr Gething tweeted.
“A welcome shift from the UK Government that matches our position.”
