The World Health Organisation has warned the UK must be willing to reverse any decision to end the lockdown if needed.
The health body said any easing of lockdown measures must be handled "extremely carefully" to avoid a new surge in cases and deaths,.
Director-General Tedros Adhanom Ghebreyesus said in a virtual briefing :"The risk of returning to lockdown remains very real if countries do not manage the transition extremely carefully and in a phased approach.
"The COVID-19 pandemic will eventually recede, but there can be no going back to business as usual
"We cannot continue to rush to fund panic but let preparedness go by the wayside.
"As we work on responding to this pandemic, we must also work harder to prepare for the next one"
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Dr Catherine Smallwood, senior emergency officer at WHO Europe, told the organisation's virtual briefing that a thorough risk assessment needed to be carried out before any lockdown measures were eased - in the UK or elsewhere.
She said relaxations needed to be "done in a step-by-step manner, that it is gradual and it is cautious", with sufficient time given to assess the impact on new cases.
She said the transition out of lockdown needed to be "flexible and adaptable", with governments prepared to reverse the decision where needed.
Hans Kluge, Regional Director of WHO Europe, also warned the situation remains "fragile" and said countries like the UK could "quickly relapse if basic measures are not scaled up".
He said: "It is over 3 months since the novel coronavirus gained a foothold in our Region, over 2 months since Europe first documented community transmission, and just over 1 month since we observed the virus move east across the European Region.
"With a total of 1.6 million cases and almost 150,000 deaths, the European Region accounts for 45% of cases and 60% of global deaths associated with COVID-19.
"I am sorry for the loss of every grandmother, grandfather, mother, father, sister, brother, son or daughter during these times."
He continued: "The situation remains very fragile and could quickly relapse if the basic measures are not scaled up, their surge maintained and if the transition is not planned carefully and gradually.
"The past month of restrictive measures and lockdowns have understandably bred stress and anxiety. Social networks are disrupted, and insecurity and financial strains with jobs in jeopardy."
A 50-page draft report of how the UK could exit lockdown has been drawn up by the government.
Brits will be able to enjoy unlimited exercise outside from Monday, according to a draft 50-page plan to take the country out of lockdown.
Since March 23 exercise outside the confines of the home has been limited to just one hour a day, though it is expected to be one of the first restrictions lifted by Boris Johnson.
Britain's route out of coronavirus lockdown is a five-stage plan staggered over the next six months.
Boris Johnson will set out his “roadmap” on Sunday. He said the first steps will happen the next day “if we possibly can”.
The Mirror understands a draft 50-page plan has been drawn up to get the country back to normal.
The Government's blueprint aims to to relax the lockdown in staggered steps between now and October.
From Monday it is also likely employees will be encouraged to return to workplaces that have stayed open through- out the lockdown if safe.
