Spain and Portugal's football federations are to launch a joint bid for the countries to host the 2030 World Cup.
The FAI have previously committed to exploring the possibility of launching a joint bid to host the tournament along with the UK countries.
There has also been interest from Morocco in hosting the tournament, and talk of a joint bid by Uruguay, Argentina, Paraguay and Chile.
A statement from the Royal Spanish Football Federation (RFEF) said: "The president of the RFEF and vice president of UEFA, Luis Rubiales, and the president of the Portuguese Football Federation and vice president of UEFA, Fernando Gomes, ratified today in Lisbon an agreement to promote the joint candidacy for the organisation of the 2030 World Cup, establishing strategies for the international projection of both federations and countries."
Rubiales said: "This agreement means an important step for this common project of federations, but also for the countries. Soccer, sport, is a magnificent tool to inject strength and will to overcome in these moments of great difficulty.
"Few things can generate more illusion than the opportunity to organise a World Cup and we cannot think of a better partner than Portugal. We go hand in hand with the Portuguese Federation."
The agreement was signed at the Jose Alvalade Stadium in Lisbon on Wednesday ahead of the international between Portugal and Spain there in the evening.