Jose Mourinho has insisted that Manchester United will continue to fight for the Premier League title until it becomes mathematically impossible for them to overhaul Manchester City after the 2-1 defeat to their arch-rivals at Old Trafford.

The home side were thoroughly outclassed as goals from David Silva and Nicolas Otamendi extended City's lead at the top of the table to 11 points, with Marcus Rashford scoring a consolation goal for the Red Devils on the stroke of halftime.

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Mourinho conceded that City's advantage in the title race is "a very good one", but was adamant that United would continue fighting to close the gap – starting with the midweek game against Bournemouth.

"[City] are a very good team. They are lucky, they have good decisions in their favour, but Tuesday is another day of the Premier League," the Portuguese coach was quoted as saying by United's official website.

"I am sure all of us – Chelsea third and the others in fourth, fifth, sixth – I'm sure that everyone is going to fight for points and fight to reduce the distance, which is a normal thing in the fight for the championship."

Mourinho voiced his displeasure at referee Michael Oliver for not awarding his team a penalty after Ander Herrera went down under the challenge of Otamendi late in the second half.

"I think [the referee] had a good performance but it's a clear penalty," he said. "It's a clear penalty and I feel sorry for Mr Oliver because he had a good performance. He's a human being and tried his best. He was very committed to having a good match, which I think he had.

Jose Mourinho
Jose Mourinho's Manchester United are 11 points behind Manchester City Getty Images

"You can speak about anything you want. You can bring any football theory, you can bring the stats, the ball possession, you can bring everything you want, but... it is a huge penalty in the crucial moment of the game."

Reports say the aftermath of the derby clash was marred by ugly clashes between both sets of players and support staff in the vicinity of the visiting dressing room at Old Trafford.

Jose Mourinho Manchester United FC Manchester City FC Premier League