King Juan Carlos has urged Spanish players to "fight" for victory in today's semi-final but rated their chances only at "50-50".
Asked to predict the score, he said, "I don't know but I think they re a strong team and so we have to fight for it.
"We are playing well, we are in the semi-finals and I hope we will also have the luck that we need and we will win."
Asked if he was confident of victory over an attacking Russian side after beating them 4-1 in their opening match, Juan Carlos said, "Yes, 50-50".
The Spanish monarch was speaking to Reuters on the sidelines of a ceremony to unveil a new European military plane, the A400M airlifter, which is being built in Seville.
Juan Carlos, a keen sports fan, went down to the changing rooms to congratulate Spanish players on reaching the semi-final when they beat Italy on penalties on Sunday in Vienna.
Spain have not won a major soccer trophy since 1964, the European Championship.
Prince Felipe of Spain, heir to the Spanish throne, and his wife Princess Letizia will be watching today's match but Juan Carlos was not on the UEFA list of VIP guests at the ground.