The 22-year-old is one of Manchester United's top targets this summer, and the club have offered to triple the midfielder's wages should he move to Old Trafford.
Thiago has a buyout clause of €18 million [£15m] until July 31 after not playing the required number of minutes stipulated in his contract last season, and United had appeared on the verge of a deal.
| TRANSFER TALK
|8/1||Bayern Munich are 8/1 with William Hill to sign Wayne Rooney
"I asked Sammer and Rummenigge for the player. I don't know what happens in future but I would like to get him," he told reporters.
"Thiago is the only player I want, that's what I told them. 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 want him] Because he is from Barcelona. I know him, he is really good. He has been with me at Barcelona B.
"I don't think [signing another midfielder] will be a problem. I spoke to club about my project and told them why I want Thiago Alcantara.
“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.”