La Roja are currently level on points with Les Bleus at the top of their group. and Busquets believes whoever wins the clash between the two in Paris on Tuesday is likely to also win the group.
"I don't know if it will be a final against France, but it will certainly be a key game," he told a press conference on Wednesday. "The team that gets the three points from that game will be very well positioned.
Busquets also played down any suggestions that old divides between Real Madrid and Barcelona players would have been reopened by their recent clashes, but did accept that the loss of the captains of both clubs to injury is a big miss. Iker Casillas has just returned to training following a hand injury, while Carles Puyol recently underwent knee surgery. However, Xavi has joined up with the squad despite his troublesome hamstring, and Busquets said his presence is a sign of how important these two games are.
He said: "Here the players of Barcelona and Real Madrid are all in the same ship. We know how to differentiate between what happens at club level and what happens with the national team.
"If Iker and Puyol had the same chance of being here then they would be, just like Xavi is. We are playing for a World Cup."
Garcia eager to seize opportunity
While Busquets is certain to start both games barring injury, Manchester City midfielder Javi Garcia is a relative newcomer to the squad and he is looking to make the most of his opportunity.
"We know that to get into the national team is very complicated," he said. "There are players of a great level that have been left out.
"You can't be complacent. I have come to take advantage of my opportunity, to fight to continue being included, and to help the team qualify for the World Cup."