People who live in areas of the UK with high levels of coronavirus will be prevented from travelling to Wales by the Welsh government.
Under regulations currently being prepared, anyone living in areas with high levels of coronavirus in England, Scotland and Northern Ireland will not be able to travel to Wales.
First minister of Wales Mark Drakeford said the action was being taken after his requests for the measure were ignored by Boris Johnson.
The new restrictions are planned to come into force at 6pm on Friday.
The plans will bring people elsewhere in the UK in line with measures currently in place in the 17 areas of Wales under local lockdown restrictions.
Under those rules, people must not enter or leave an affected area without a reasonable excuse such as work or education.
But currently, people living in Covid-19 hotspots elsewhere in the UK are free to enter areas of Wales not under restrictions where levels of the virus are low.
Mr Drakeford told the Welsh Parliament that Mr Johnson had not replied to two letters asking for such travel restrictions to be imposed in the worst-hit areas of England.
“I have therefore asked for the necessary work to be brought forward, which would allow for devolved powers to be used to prevent people from travelling into Wales from high-prevalence areas of the United Kingdom,” he said.
He said it was “important” to emphasise that it was not an issue regarding the border between Wales and England but a “matter of fairness”.
“We’ve already heard from the First Minister of Scotland and she’s eager to support what we’re trying to do here. Now is the time for the Prime Minister to do the same thing,” Mr Drakeford told the Senedd.
“If he isn’t willing to do so then the timetable is for us to use the powers in Wales by the end of the week.”
Plaid Cymru leader Adam Price welcomed the Welsh Government’s plan.
Mr Price said the announcement was “long overdue” and was necessary to protect people in Wales.
“We now need a clear timetable for exactly when the draft legislation will be ready to publish, the proposed timescales and plans for implementation and how this is to be communicated across the UK,” Mr Price said.
“With half term arriving for much of England next week, timing is now critical.”
