Rumours that Rooney could miss Sunday's clash had begun to circulate after media reports said he limped away from training on Monday with a foot injury. Defiant Pellegrini won't change ahead of derby
Manchester United manager Louis van Gaal told reporters on Friday, however, that Rooney would feature, but fellow striker Radamel Falcao would not be available.
"Falcao is still injured," he said.
"Rooney shall play, he is my captain,” he added.
After scoring a late equalising goal in their last two games, against West Bromwich Albion and Chelsea, United believe they go into Sunday's match in better heart than rivals City, who have recently surrendered a 2-0 halftime lead in drawing with CSKA Moscow, then lost to West Ham United in the league and Newcastle United in the Capital One (League) Cup.
"What we have seen of City in the last few matches was not so good," said Van Gaal, who believes his team can win his first Manchester derby.
"That is our goal, to win. It is possible, we are growing,” he added.
"This is the biggest derby that I shall manage. It is one of 38 (league) matches we have to play, but for the fans it is unbelievably big as a rivalry and I have felt that also with a lot of the players in the squad, but also especially with (assistant manager) Ryan Giggs,” the Dutchman said.
"When he presented the analysis on City, I felt more tension with him. It was good to see. I have to analyse and prepare for all games in the same manner, but for the players and the fans it is different,” he further added.
Rooney, who has 11 derby goals to his name in 22 games, has missed United's last three matches through suspension after being sent off against West Ham on September 27.
The late point earned by Robin van Persie's last-minute equaliser at home to Chelsea on Sunday took them into eighth place but a win would move them only one point behind their neighbours, who are currently third.
Meanwhile, Manchester City manager Manuel Pellegrini insists he will not change the way his team play despite suffering two defeats in a week and losing playmaker David Silva ahead of Manchester United's visit on Sunday.
The Premier League champions have endured an indifferent start to the season and Pellegrini has come under increasing pressure after expressing concern over his side's form earlier this week.
A 2-1 loss at in-form West Ham United on Saturday left them third in the table on 17 points, six adrift from leaders Chelsea, before the defence of their League Cup title ended prematurely with a surprise 2-0 home defeat to Newcastle United on Wednesday.
The beleaguered Chilean remained defiant, however, in the face of United's trip to the Etihad Stadium, insisting that his out-of-sorts team do not need to change much even if they will be without Silva, who will be missing for up to a month after injuring his knee.
"David is a very important player but I always say the same thing. We have a squad and we have to replace him with another player," Pellegrini told a news conference.
"I think that we can play faster than we are doing. But still, I remember the games against the Newcastle and West Ham, the best player was their goalkeeper,” he added.
"If I think back to a year ago, I was answering the same questions. When we didn't win away for the first six games -- it was the same questions I just answered now. I will continue to play the same way,” he further said.
Pellegrini got his first taste of a Manchester derby at the Etihad last season and an excellent performance from his side ended in a resounding 4-1 victory.
The City boss indicated that a similar performance in the fixture on Sunday could galvanise his team, as it did last year.
"The game we played here, the first one at the Etihad (last year) was in a moment where I was new here, where maybe there were a lot of doubts about the result but I never changed my mind in the way we have to play against any other team," he said.
"I remember the exact moment when I told the players to work in exactly the same way. That was an important moment and we really played very well,” he added.
"It was three points, like every other game. For supporters it's a special game and we know that. We know what it means to win against Manchester United,” the former Real Madrid manager said.
"It doesn't depend on what we do in the games before the derby, it's important for us to play well against Manchester United. We are a team and we need top players with top performances all the time,” he added.
Silva will be absent, but City expect to have midfield powerhouse Yaya Toure fit for Sunday.
Rumours that Rooney could miss Sunday's clash had begun to circulate after media reports said he limped away from training on Monday with a foot injury.
Defiant Pellegrini won't change ahead of derby