Welsh ministers are in emergency talks to discuss “serious concerns” over the spread of a new strain of Covid-19.
First Minister Mark Drakeford took part in a call with representatives of the UK’s devolved nations after a surge in cases.
Prime Minister Boris Johnson is due to give a press conference at 16:00 GMT on Saturday in response to rising case rates in parts of England.
It comes as rules are due to be relaxed for over the Christmas break.
England’s chief medical officer Prof Chris Whitty said government advisers “consider the new strain can spread more quickly”.
The BBC understands Mr Johnson is about to announce tougher measures for London and south east England.
Mr Drakeford has already announced a Wales-wide lockdown, with people being told to “stay home”, which will begin on 28 December, when the Christmas relaxation of rules ends.
In a tweet, the first minister said: “I attended a four nation call earlier today to discuss serious concerns over the spread of a new Covid variant.
“I will chair a meeting of the Welsh Government Cabinet at 2pm today.”
Scotland’s First Minister Nicola Sturgeon has warned more preventative action may be “necessary” to stop the strain taking hold.
In Wales rules for who can meet over Christmas had already been tightened, following a surge in coronavirus cases in communities in recent days.
Three households can meet in England, Scotland and Northern Ireland between 23 to 28 December, following a UK-wide agreement.
But in Wales this has been reduced to two households, with a further single person household allowed to meet with them, with the rule made law.