The Health Minister has cooled the prospects for music festivals or sporting fixtures with crowds taking place in Wales this summer.
Vaughan Gething said he would be "delighted to be wrong" if large-scale events are able to go ahead, but that scientific and medical advice did not suggest it would be possible.
Mr Gething also described Boris Johnson's announcement that all coronavirus restrictions could be lifted in England by June 21 as "optimism" rather than "data-led".
He added that he had doubts over Mr Johnson's plan to resume international travel in and out of the UK by May 17 at the earliest.
On Wednesday, the Health Minister appeared at the Welsh Parliament's Health, Social Care and Sports Committee, where he was asked how the Prime Minister's road map out of England's lockdown was affecting public expectation in Wales.
Mr Gething said: "Whatever the Prime Minister says makes a big difference across the UK in terms of public messaging and understanding, now more than ever.
"I don't see a path to re-normalising international travel in May. And the third week of May is a long time in the course of a pandemic. And the June date, again I think that is optimism rather than taking a data-led approach.
"I'd love to be in a position where you can have music festivals and full stadiums, whether you're watching (British and Irish) Lions' games, or if Euro 2021 is moved here. That would be fantastic.
"If we could do that I'd be delighted - one of those occasions where you'd be delighted to be wrong.
"But that isn't the advice that I see."
Referring to chief medical officer Frank Atherton and chief scientific advisor Rob Orford, Mr Gething said: "That isn't the advice that either Dr Orford or Dr Atherton are giving, that actually we can tell you with some confidence to allow you to go in public to say that these things will be possible in June."
He added: "The step-by-step approach is the right thing to do. We're not building up people's hopes and expectations, because if you can't then do that, there's a massive loss of trust.
"And that potentially affects people's willingness to do the right thing if we do need to carry on living with restrictions to keep us all safe."
A summer ban on large crowds would come as a blow to organisers including those of the Green Man, held in the Brecon Beacons, who said last week they were "planning away" after the Welsh Government suggested possible dates for easing restrictions.
In January Wales' Ceredigion National Eisteddfod festival was postponed for the second successive year, with organisers saying at the time it was becoming "increasingly clear" that holding the summer festival would not be possible.
The Welsh Government's next Covid-19 review is on March 12, although First Minister Mark Drakeford has only outlined possible easing of restrictions as far as Easter when the tourism industry is expected to reopen for self-contained accommodation.