Welsh ministers say they cannot rule out imposing another firebreak lockdown early in 2021 if Covid-19 starts spreading quickly again at Christmas.
Economy Minister Ken Skates urged people to stick to the rules during Wales’ two-week lockdown from Friday.
Scientific advisers say it is possible that the R rate could drop from 1.4 to 0.8 over that period.
However, the impact of the firebreak will not be known until some time after the lockdown has ended.
The R rate is the number of people that one infected person will pass the virus to, on average.
Mr Skates told the Welsh Government’s coronavirus news briefing on Tuesday that lowering the R rate to that extent “would, in itself, buy us enough time, give us the headroom, to get through to Christmas and the new year”.
“But of course we could not rule out the possibility of introducing another firebreak if over the Christmas period transmission rates increase dramatically,” he said.