Reviewed coronavirus lockdown measures in Wales will be announced by the Welsh Government later.
First Minister Mark Drakeford is likely to take a cautious approach on how and when minor adjustments to the stay at home restrictions could be made.
His focus is on ensuring the R rate of transmission – the measure on how contagious viruses are – is not allowed to rise to uncontrollable levels.
The doctor in charge of Wales’ Covid-19 response expects few changes.
Dr Giri Shankar, of Public Health Wales, fears there is “a very high chance” that progress in curbing the spread of coronavirus could be undone if lockdown measures are relaxed.
UK public health bodies want the R number to stay below one – and experts believe Wales’ value between 0.8 or 0.9.
Dr Shankar told BBC Radio Wales that PHW want to be “absolutely clear” that Wales’ R value “does not increase to the extent that it becomes unmanageable”.
“Even a minor increase in R value may look numerically small, the impact of what that translates to at a population level can be significant,” said Dr Shankar, PHW’s Covid-19 incident director,.
“And we’re talking about hundreds of additional deaths as a result of minor increases.
“We have made significant gains by continuing with the lockdown effort – and whatever gains we have made should not be reversed. And there is a very high chance that it will be reversed if there is uncontrolled release of lockdown.”
The results of the Welsh Government’s lockdown review will be announced in Friday’s lunchtime briefing.
It comes after Downing Street said Wales and the other UK nations may move differently on easing the restrictions.
Welsh ministers met twice on Thursday to discuss their formal review of the Welsh stay-at-home regulations, which must be completed every three weeks.
Their announcement will be made two days ahead of when Prime Minister Boris Johnson is expected to set out the plan for England.
Plaid Cymru leader Adam Price urged the first minister and prime minister “not only to retain the policy, but ensure there is no change in the perception that for now people must continue to stay home to save lives”.
“We hope, above all, that you will be able to come to an agreement based on a parity of respect for both nations and the lives of each one of their citizens,” he said.
Education Minister Kirsty Williams has already said schools in Wales will not re-open on 1 June, following what she called “speculation” around announcements in England.
Welsh Government officials have asked people to stay at home over the bank holiday weekend.
Tensions between the Welsh and UK governments over the lockdown regime emerged on Thursday, after speculation arose that restrictions could be eased in England.
A Guardian article claimed that Mr Drakeford had not been made aware of what the prime minister was planning to do in England.
The pair later took part in a joint call with the first ministers of Scotland and Northern Ireland.
A Downing Street spokeswoman said Boris Johnson “reiterated his commitment to continuing” the UK-wide approach to tackling coronavirus “even if different parts of the UK begin to move at slightly different speeds”.
“Those decisions will be made based on the science for each nation,” the spokeswoman said, in a read-out of the discussion.
Lockdown laws in Wales, Scotland and Northern Ireland are devolved, with the nations’ national governments in charge of the public health legislation.
So far the coronavirus lockdown has remained broadly similar across the UK, with some differences – Wales has a different fine structure, rules on two-metre social distancing at work and different rules on exercise.
The Welsh Government could choose to make further changes from England and elsewhere – but has said it prefers to take decisions alongside the other four nations.
Some UK newspapers suggested the rules on exercise in England could be relaxed and more people encouraged to return to work.
But ministers sought to play down the report – Foreign Secretary Dominic Raab said they were not a reliable guide and the prime minister said the government would proceed with “maximum caution”.
The stories also prompted concern in the Welsh Government that they did not make clear the Welsh lockdown rules were for Cardiff ministers to determine.
It issued a statement saying some of the reporting “is confusing and risks sending mixed messages to people across the UK”.
Divergence ‘needs to be backed by evidence’
In an interview with BBC Wales, Welsh Secretary Simon Hart speculated that the “UK government and Welsh Government are much closer aligned than perhaps it looks at the moment”.
Mr Hart said if there was a divergence “it would need to be really, obviously, supported by evidence”.
He said he was not sure “that evidence had been seen by either Mark Drakeford or I at this stage”.
The Welsh secretary added he thought the relaxation measures announced for England on Sunday would be “modest”.
Plaid Cymru’s Westminster leader Liz Saville-Roberts met the prime minister with other Westminster opposition party leaders on Thursday
Before the meeting a Plaid Cymru source suggested Welsh ministers did not seem to be ready for lockdown to be lifted.
Referring to an estimate in a Public Health Wales report of the number of tests a day that may be needed for tracking coronavirus, the source said: “The Labour Welsh Government isn’t even hitting a thousand tests daily, when 30,000 a day are needed according to the experts, and dozens of people are dying everyday in Wales.”
Analysis by Felicity Evans, BBC Wales Political Editor
The Welsh Labour Government is in a particularly difficult position over whether or not to diverge from England over easing the lockdown – and the primary reason for that is geography.
Scotland has a natural buffer zone – its border with England is very sparsely populated.
The Welsh/English border is a totally different story – lots of people live there and it is busy in normal times.
So imagine the problems with messaging and enforceability if there were different rules on travel or exercise in the two nations.
Downing Street seems to have accepted that some divergence around the UK is inevitable – we will find out which way the Welsh Government will go on Friday.
The Welsh Government press briefing will be on BBC One Wales and streamed live online at 12:30 BST on Friday. Mark Drakeford will deliver a first ministerial statement on BBC One Wales at 17:55 on Friday.