World Cup winner Fabregas was a youth player at Barca before moving to the Premier League club in September 2003 and the player has made it clear he wants to return to the Catalan capital.
GEAR:Get a Fabregas shirt
Local media reported on Monday that Barca's new president, Sandro Rosell, would travel to London this week to try to strike a deal but Guardiola was downbeat about the chances of success.
"I think that getting Cesc will cost a lot," Guardiola told a news conference at the club's training ground on the outskirts of the city.
"He is an important player for Arsenal," he added. "We want him to come but if Arsenal don't want to negotiate he won't."
Barca, who have already added Spain striker David Villa and versatile Brazilian midfielder Adriano Correia to their squad, have about 40 million euros more to spend on players, club officials have indicated.
As well as Fabregas, they would probably need to buy a holding central midfielder to replace the Manchester City-bound Yaya Toure.
Asked about the possibility of Zlatan Ibrahimovic leaving, Guardiola said he wanted the Swedish striker to stay but it was up to the player to decide.
Mexico captain Rafael Marquez was in the same situation, the coach added.
Ten of Barca's first-team squad began pre-season training on Monday, with internationals including Andres Iniesta, Villa, Xavi, Lionel Messi and Gerard Pique still on holiday.
