The 19-year-old centre-back has been linked with a return to boyhood club Barcelona.
"If they want him they must call Txiki," Guardiola said after the 5-0 victory over Newcastle on Wednesday night.
"We are going to try to convince him to stay here for many, many, many years.
"I'm confident he will stay but at the end of the day it's his decision. He knows we want him.
"But it is similar to Leroy [Sane]. We wanted him but he didn't want to stay and we cannot do anything else.
"He knows, his agent knows, and his family knows that we want him. He's young and if Barcelona want him, they have to call Txiki."