The vastly successful 41-year-old - whose contract expires at the end of June - had a three-hour meeting with club president Sandro Rosell on Thursday to discuss his future, the reports said.
Barca did not confirm any Guardiola news conference or announcement was scheduled for Friday but a source close to the club, who asked not to be identified by name, told Reuters Guardiola had informed Rosell of his decision to move on.
The source added that while he could change his mind at the last moment after talking to his family, it looked unlikely he would extend his four years in charge.
Rosell is desperate to persuade Guardiola to stay on and the longer he has delayed his decision the more speculation has grown he might be lured to another club with reports linking him to the Chelsea and Inter Milan jobs, among others.
Other reports suggested he was in line to become the next England manager or that he was planning to take a sabbatical.
The odds on Guardiola taking over from Fabio Capello at the helm of the England team narrowed sharply on Thursday. One British betting house quoted him as 22/1 earlier on Thursday and those odds fell to 14/1.
The former Barca and Spain midfielder has preferred to renew his contract on an annual basis and waited until February 8 last year before agreeing a new deal.
He went on to capture a third straight La Liga title and a second Champions League crown, as well as the Spanish and European Super Cups and the Club World Cup, and has led Barca to 13 trophies since taking over in 2008.
However, his team were knocked out of the semi-finals of the Champions League by Chelsea on Tuesday and their three-year stranglehold on the La Liga title is poised to come to an end as bitter rivals Real Madrid have a seven-point advantage at the top of the standings with four games left.
Barca's one remaining chance of silverware this season is in the King's Cup and they play Athletic Bilbao in next month's final in Madrid.
