The inaugural Rainbow Cup will no longer have cross-over matches between sides in the northern and southern hemisphere after UK officials failed to approve travel for South African teams due to COVID-19 restrictions.
The competition will continue with dual events that will see teams from Wales, Scotland, Italy and Ireland play in one pool, and the four South African sides compete in another in a blow to the Springboks' preparations for the British & Irish Lions series later in the year.
"No stone was left unturned to try and find a solution to the challenges - including basing our teams for 10 days in locations in the Middle East or Europe. But the pieces of the jigsaw would not fall into place in time to allow us to put those plans into action," SA Rugby CEO Jurie Roux said in a statement.
South Africa is on the UK's red list of countries in terms of COVID-19 risk, which meant players and officials would face tougher restrictions.
It is a financial blow for cash-strapped SA Rugby, but plans for the Bulls, Lions, Sharks and Stormers to enter an expanded PRO16 competition against European opposition in the 2021-22 season continue.
"We are looking forward to the two Rainbow Cup competitions, and in due course sharing our intentions about our future partnership that will be boosted by the experiences and project-planning involved to this point ahead of the 2021-22 season," PRO14 chief executive Martin Anayi said.
A revised fixture list for the Rainbow Cup will be released in due course, officials added.