The prime minister will unveil a five-stage coronavirus warning system as part of a gradual easing of the lockdown.
Boris Johnson will also leave behind the old “stay at home” slogan and instead tell people to “stay alert, control the virus and save lives“.
A five-stage system administered by a new “joint biosecurity centre” will detect increases in COVID-19 infection rates and judge how strict lockdown measures and social distancing rules should be locally in England.
With the alert levels ranging from green (level one) to red (level five), Mr Johnson is expected to say the nation is close to moving down from level four to three.
The UK’s lockdown was introduced on 23 March to try to contain the spread of COVID-19 and, by law, it must be reviewed every three weeks, with the next deadline falling on Thursday.
But on Sunday, Mr Johnson will chair a meeting of the emergency Cobra committee before his pre-recorded address airs at 7pm, with some changes potentially taking effect as early as Monday.
He is expected to tell people who cannot work from home that they can return to their workplaces while following social distancing rules.
Garden centres are likely to be allowed to reopen and the limit of one type of exercise a day will be relaxed, while there will be tougher fines for those who break the rules.
There are also reports that ministers are planning a 14-day compulsory self isolation period for people arriving at UK airports from any country apart from the Republic of Ireland.
A larger 50-page document is to be revealed on Monday which will outline how the UK economy will be revived after the virus outbreak forced widespread business closures.
But there is concern that many workers might not be willing to return to work yet, as figures suggest the coronavirus death toll for the UK sits at more than 30,000.
A scientific adviser to the government told The Sunday Times that the UK could still suffer more than 100,000 deaths by the end of the year if the lockdown is relaxed too quickly.
Union leaders have said they will no recommend their members return to work until their safety can be assured.
In The Observer, Unison, Unite, the GMB, Usdaw and the Trades Union Congress wrote that workers needed to know that “ministers have listened and that we stay safe and save lives at work too”.
Mr Johnson told the Sun On Sunday: “You have very few options on the climb up – but it’s on the descent you have to make sure you don’t run too fast, lose control and stumble.”
Meanwhile, Transport Secretary Grant Shapps has announced a £250m package to boost cycling and walking, warning that some forms of public transport will only be able to run at 10% capacity under social distancing rules.