Five of the 31 tanks have already been lost to Russian attacks in Ukraine, where the use of surveillance and hunter-killer drones had made it difficult for them to operate.
Socialist Prime Minister Pedro Sánchez left Spain in suspense after announcing he may step down because of what he called an "unprecedented" smear campaign against his wife.
Prosecutor Rafael Curruchiche said that the complaint filed by an unidentified foreigner had raised serious concerns because it involved allegations of abuse of children.