Reports emerged on Thursday claiming that the European Champions had beaten Manchester United to the 22-year-old's signature, and Guardiola confirmed that he had asked the club's board to sign the Spanish playmaker.
Asked why he would like Thiago to join him at the Allianz Arena next season, Guardiola said: "Because he is from Barcelona. I know him, he is really good. He has been with me at Barcelona B.
"Thiago is the only player I want, that's what I told them," he said. "It'll be him or no-one. We have many players but we the need the special [quality] that Thiago Alcantara brings.
"The club will decide. I told them my opinion. I don't think [adding another midfielder] will be a problem. I spoke to club about my concept and told them why I want Thiago Alcantara."
Thiago was part of the Spain Under-21 side that won the European Championships this summer, scoring a hat-trick in the final against Italy.