Spain and Portugal players wore 'Vamos 2030' T-shirts before Friday's friendly which finished 0-0 in Madrid
Spain and Portugal will make a joint bid to host the 2030 World Cup.
A symbolic ceremony was held before the nations' Euro 2020 warm-up which ended 0-0 at Madrid's Metropolitano Stadium.
Spain's King Felipe VI and Portugal president Marcelo Rebelo de Sousa were present as each nation's prime minister signed an agreement to support the bid.
Both teams wore T-shirts bearing 'Vamos 2030' before the friendly, which marked the centenary of Portugal's first international – also against Spain.
"The governments of Spain and Portugal wish to express their desire and commitment to host the 2030 World Cup," the agreement said.
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Fernando Gomes, president of the Portuguese Football Federation, and his Spanish counterpart Luis Rubiales, ratified an agreement signed last October to promote a joint bid.
"A message to the [other] national federations: if you give us your trust, when you come to our countries you are going to find an unforgettable experience," Rubiales said on Friday.
The 2022 World Cup will be held in Qatar while Canada, Mexico and the USA will be joint hosts in 2026.
Fifa plans to select the 2030 host in 2024.
Spain and Portugal could face competition from other joint bids under discussion: one from the UK and the Republic of Ireland, and one from Argentina, Uruguay, Paraguay and Chile, aimed to coincide with the centenary of the first World Cup in Uruguay.
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