Sergio Aguero swooped late to edge an FA Cup thriller at Swansea City in Manchester City's favour on Saturday.

Substitute Aguero beat Swansea keeper Kristoffer Nordfeldt with a diving header off Bernardo Silva's low cross at the end of a superb move in the 88th minute.

Replays showed the Argentina striker was marginally offside but the video assistant review system was not in use at the Liberty Stadium, despite having been used in City's third and fourth-round ties at their Etihad Stadium home.

City had levelled in contentious circumstances too when Cameron Carter-Vickers was judged to have tripped replacement Raheem Sterling in the area and Aguero's penalty hit the post before rebounding in off Nordfeldt for an own goal.

Defeat was harsh on the impressive hosts, who led 2-0 inside 30 minutes through Matt Grimes' penalty and Bersant Celina's spectacular second.

"I'm sorry it was offside. I don't understand why VAR is not used in this competition at this stage. Hopefully next season this won't happen," City boss Pep Guardiola told BBC Sport.

"The penalty was really lucky but you need it, especially when you're in four competitions."

Guardiola continued: "The most incredible thing after what we achieved last season is in this stage we are fighting for everything.

"The most important for the club - more than winning one title - is having the mentality to be there until the end and fight for the titles in this stage of the season.

"That's important because for the future, for the new players and managers who are coming, they will learn from this group of players, and this group of people, that we never give up and fight for every single game and title until the end."