ESPN reported earlier this month that the Portugal international had handed in a transfer request due to his desire to play in the Champions League.
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Ronaldo held talks at United's training ground on Tuesday -- accompanied by agent Jorge Mendes -- after missing the club's preseason tour of Thailand and Australia, citing personal reasons.
Ronaldo appeared to signal his availability for Sunday's game in an Instagram post on Friday.
"Sunday, the King plays," wrote Ronaldo on a fan page's post that highlighted his absence from the squad.
Ronaldo has a year left on his United contract and Ten Hag said earlier this month that he was looking forward to working with the Portugal captain who was their top scorer last season with 24 goals in all competitions.
United, however, finished sixth in the league to miss out on Champions League qualification and will play in the second-tier Europa League this season.
Atletico Madrid and Bayern Munich have both publicly distanced themselves from a move for the former Real Madrid and Juventus star. Another reported suitor, Chelsea, have also ruled out a deal, sources told ESPN.