The list of potential bidders to have expressed their initial interest in staging one of the tournaments grew to a dozen on Monday when FIFA confirmed the late entry of Egypt and South Korea.
World soccer's governing body is due to publish the final list on Tuesday. Barring any further late additions it should comprise five bids from Asia, four from Europe, two from the Americas and one from Africa.
There is confusion though over FIFA president Sepp Blatter's opposition to joint bids and the extent to which his views reflect official policy.
Blatter told reporters at a meeting of the South American Football Confederation last week that "as soon as there is a (sole) candidacy or three or four relevant candidacies, we are directly going to reject the double candidacies".
"Countries capable of staging the event alone should do so," added the spokesman in a clarification that will increase pressure on Spain to ditch its planned partnership with Portugal.
If the European and Asian members of FIFA's executive committee fail to agree on the strongest candidate in their regions during the final vote in December 2010, the United States, Mexico or Egypt could benefit.
South American countries were unable to put themselves forward for either tournament due to Brazil's scheduled hosting of the 2014 version.
Following South Africa's staging of the 2010 World Cup, African nations were free to apply for the 2022 event but Egypt look set to be the only ones to do so.
The bidding process has been further complicated by FIFA's decision to offer up two World Cups simultaneously.
Final bid dossiers have to be submitted by May 2010 with FIFA's executive committee casting its decisive votes seven months later.
