Several British and Spanish newspaper had reported that Arsenal had agreed a transfer deal that would see the Spaniard fulfil his dream of returning to the club he left as a 16-year-old in 2003.
But Guardiola said: "He's not here yet. 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."
European champions Barcelona had already failed with an offer of around £30 million (34.4 million euro), and an improved reported bid of 29 million euros plus six million euros in future add-ons also failed to tempt the Gunners.
The British press reported however that Arsenal were finally ready to accept a 36-million-euro offer, with Spanish sports daily Marca putting the deal closer to 40 million euros, of which six million euros would depend on results.
The 24-year-old has been omitted from the Arsenal squad for Saturday evening's match at Newcastle.
And Barcelona defenders Carles Puyol and Gerard Pique sent messages on their Twitter accounts on Friday welcoming Cesc before any official announcement.
"Welcome home, happy to have you here @cesc4official," Puyol tweeted, addressing his message to Cesc's Twitter account. "@cesc4official, we have got him," tweeted Pique.
Spanish sports daily AS reported that Fabregas' departure had been pushed back until Sunday after he received a call on his way to the airport as Guardiola feared his arrival would upset preparations for Sunday's SuperCup tie against Real.
Arsenal manager Arsene Wenger on Friday declined to confirm reports that Fabregas and France's Samir Nasri were set to be sold on the eve of the Premier League campaign.