The 22-year-old Italian-born midfielder has been widely tipped to move to Old Trafford this summer, but Guardiola has now made the Spain international his priority target.
"I want Thiago Alcantara," the new Bayern manager said. "I have asked. I don't know what will happen.
"I don't think that will be a problem. I spoke to club about my concept and told them why I want Thiago Alcantara.
"Thiago is the only player I want, that's what I told them. It will 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. Nobody will leave Barcelona, unless they feel they won't play much. He wants to play. That's why I proposed him to the club."