Spain is due to sign a framework deal to sell Saudi Arabia warships worth around 1.8 billion euros ($2.2 billion) on Thursday, a Spanish Defense Ministry source said.
Under the agreement, Spanish state-owned shipbuilder Navantia will sell five small warships, Spain's army will train Saudi military personnel and contractors will build a naval construction center in the kingdom, the source said.
The deal will be signed in Madrid, where Saudi Crown Prince Mohammed bin Salman is on a state visit, the source added. An industry official confirmed the details of the agreement, though Navantia declined to comment.
Campaign groups Amnesty International, Spain's FundiPau, Greenpeace and Oxfam have called on Spain to stop selling military equipment to the Saudis, accusing the kingdom of abusing rights - charges it denies.
Prince Mohammed, who serves as defense minister and controls economic and energy policy, was welcomed by Spain's King Felipe VI at the Zarzuela palace on the outskirts of Madrid.
He also met Defense Minister Maria Dolores de Cospedal, and lunched at the royal palace with Prime Minister Mariano Rajoy.
The two sides have been negotiating the warship deal since 2015, and the final agreement between the Saudi defense ministry and Navantia would take longer to complete, the ministry source said.