Barca appeared to be closing in on the protracted capture of Fabregas on Friday after a club spokesman suggested a deal was "hours away" from being announced.
A deal was expected to be completed over the weekend and that Fabregas would be in attendance for the first leg of Barca's Spanish Super Cup tie against Real Madrid on Sunday.
However, Guardiola is understood to have told Fabregas to delay his flight out to Spain in order to avoid upsetting Arsenal as talks continue over a deal.
Guardiola has now confirmed that the discussions are ongoing and appears optimistic Fabregas will eventually complete his return to the Nou Camp.
"He's not here yet," said the Barca coach.
"According to the information we have from club bosses negotiations are very advanced but there is still a document missing to confirm.
"The prospects are good, but he's still an Arsenal player. Otherwise I would confirm it."
Fabregas initially left Barca as a 16-year-old to join the Gunners in 2003 and he has been a mainstay of Arsene Wenger's plans.
He was wanted by his former club last summer, but Arsenal resisted offers for their captain, who was a 2010 World Cup winner with Spain.
However, it now appears that Gunners boss Wenger is ready to relent and allow Fabregas to rejoin Barca after admitting on Thursday that he expected a quick resolution to the matter.