Cristiano Ronaldo says "the heat of the moment" got to him in the incident that led to Manchester United dropping him for Saturday's game at Chelsea.

The Portugal forward left Old Trafford before the end of Wednesday's 2-0 win over Tottenham - for which he was an unused substitute.

"I've always tried to set the example myself for the youngsters that grew in all the teams that I've represented," he wrote on Instagram on Thursday.

"That's not always possible."

He added: "Sometimes the heat of the moment gets the best of us.

"I just feel that I have to keep working hard in Carrington [United's training ground], support my team-mates and be ready for everything in any given game. 

"Giving in to the pressure is not an option. It never was. This is Manchester United, and united we must stand. Soon we'll be together again."

United say the 37-year-old remains an important part of the squad but regard this as a disciplinary matter. 

The game he will miss at Stamford Bridge is a big one, with United just one point behind fourth-placed Chelsea.

Several media outlets are reporting he refused to come on as a late sub against Spurs.

Ronaldo left the bench and walked down the tunnel in the 89th minute, even though United had only made three of their permitted five substitutions. He briefly went into the dressing room before leaving the stadium.

Manager Erik ten Hag said afterwards that he would "deal with" the issue on Thursday.

Ronaldo had also showed his displeasure at being substituted during Sunday's 0-0 home draw with Newcastle.