Monday, April 30, 2018
Hart's future is uncertain as he nears the end of his loan spell with the Hammers, with boss David Moyes insisting no decision will be made until the end of the season.
The 31-year-old has a year left on his City contract but has little chance of re-establishing himself as number one after Guardiola decided to send him out on loan.
Guardiola admitted: "I think that was the toughest decision I've made since I was a manager.
"He was an incredible professional when we were together, and there are no doubts about his quality.
"But I am here to make decisions, sometimes good, sometimes not. We will find out in the future.
"He's our player and, if he does not continue here next season, we will talk. We are going to speak with the club and will take the right decision for him."
Hart watched from the stands at the London Stadium as his parent club thumped West Ham 4-1 on Sunday.
Leroy Sane, Gabriel Jesus and Fernandinho were on target, while Pablo Zabaleta scored an own goal against his old club, as City cruised to a record-equalling 30th victory of the season.