British newspaper The Telegraph reported over the weekend that official confirmation was expected in due course, while ticket and travel packages will soon go on sale.
There had been rumours that the tour dates would be pushed back to a later stage amid plans for a global season, but the publication insists that the tour will still take place from 3 July to 7 August next year.
"We had to make a call on this now as we were running out of time," a source told The Telegraph.
"People need to move on tickets, flights and hotel bookings and it is so important to South Africa to have certainty now given the financial importance of the tour to them at a time when we are all struggling with the impact of Covid-19."
The Lions last toured South Africa in 2009 when the Springboks ran out 2-1 series victors.
British & Irish Lions' 2021 tour schedule:
3 July: v Stormers, Cape Town Stadium, Cape Town
7 July: v SA Invitational, Nelson Mandela Bay Stadium, Port Elizabeth
10 July: v Sharks, Kings Park, Durban
14 July: v South Africa 'A', Mbombela Stadium, Nelspruit
17 July: v Bulls, Loftus Versfeld, Pretoria
24 July: v Springboks (1st Test), FNB Stadium, Johannesburg
31 July: v Springboks (2nd Test), Cape Town Stadium, Cape Town
7 August: v Springboks (3rd Test), Ellis Park, Johannesburg
-Sport 24 SA