Premier League clubs have until 12 p.m. ET on Thursday to sign players before the transfer deadline.
The Catalans have until August 31 to complete any signings.
The Portuguese has overseen United's worst start to a league campaign in 26 years.
The Portuguese demanded respect after his side were thrashed 3-0 at home by Spurs.
Mourinho reportedly told friends he would have quit by now had he been in charge of any other club.
Mino Raiola joked he will have "sleepless nights" to find Paul Pogba a new club.
The relationship between the duo is said to have hit an all-time low.
French manager left Real Madrid in June after winning three consecutive Champions Leagues.
The Spanish giants could use the same approach they adopted when they signed Philippe Coutinho from Liverpool last season.
The Frenchman's agent has reportedly offered him to Barcelona.
Blues manager Maurizio Sarri has admitted he will not keep the Belgian against his will.
The Blues are determined not to lose the Belgian after failing to sign an adequate replacement.
United continue their search for a new defender, with Toby Alderweireld also on the radar.
United are set to bid for Leicester City's Harry Maguire, but could lose Anthony Martial.
Ante Rebic and Yerry Mina both on United's radar as Jose Mourinho grows frustrated at lack of signings.
Frenchman's agent said last month his client wanted to leave United over the summer.
Neymar could leave Paris Saint-Germain, while Real Madrid want Eden Hazard.
Liverpool's new goalkeeper was ever-present in Brazil's World Cup campaign.
Spanish giants say reports of a world-record bid for Neymar were false.