Spain and Portugal have confirmed their joint bid to stage the Fifa World Cup in 2018 or 2022.
The heads of the two national football federations handed over a letter to FIFA president Joseph Blatter in Zurich, promising "the best organised and most festive World Cup".
Blatter said Spain and Portugal were "two great nations who have great experience in organisation".
Spain organised the first World Cup with 24 teams (in 1982) and Portugal hosted the European championships in 2004.
Among other countries interested in hosting the 2018 World Cup are England, Australia, Japan, Mexico and Russia, while Belgium and Netherlands are mulling over a joint bid.
FIFA's executive committee will make a decision in December 2010 on which country will host the 2018 tournament.
South Africa will host the next World Cup in 2010, followed by Brazil in 2014.