MANCHESTER, ENGLAND - NOVEMBER 28:  Robin van Persie of Manchester United celebrates  as he scores their first goal during the Barclays Premier League match between Manchester United and West Ham United at Old Trafford on November 28, 2012 in Manchester, England.  (Photo by Clive Brunskill/Getty Images)

Robin van Persie of Manchester United. Photo: Getty Images

MANAGER Roberto Mancini fears Manchester City's failure to sign Robin van Persie at the start of the season will cost it the Premier League title.

Mancini revealed that he thought he had persuaded van Persie to sign for Manchester City four months before the Dutch striker was unveiled at Old Trafford in August after a £22 million ($34.3 million) move from Arsenal.

Since then, van Persie has scored 14 goals in 20 Premier League games for Sir Alex Ferguson's side, which now has a seven-point lead over the defending champions.

Manchester City's Italian manager Roberto Mancini takes his seat before the English Premier League football match between Sunderland and Manchester City at The Stadium of Light in Sunderland, north-east England on December 26, 2012. AFP PHOTO/GRAHAM STUART

Manchester City manager Roberto Mancini. Photo: AFP

Those goals, including last-minute winners against Southampton and City itself, have been worth a total of 19 points for United, and Mancini believes City could pay for missing out on the 29-year-old's signature.

''At the moment, he is the difference between us,'' he said on Monday. ''We were very close three or four months before he went to United. We wanted van Persie because we knew he was totally different from our other strikers.

''We wanted to improve our team, particularly for the Champions League. We were very close to signing him. I know what the reason was [why he did not sign] but I won't say. It was not about money.''

Van Persie said he had listened to ''the little boy inside him'' when deciding to join United on a four-year contract worth £250,000 a week - the same terms handed to Wayne Rooney two years ago.

Speaking at his official unveiling news conference, he said: ''In these situations, when you have to make a hard decision in your life, I always listen to that little boy inside me. What does he want? That boy was screaming for Manchester United.''

When pressed to explain why he thought van Persie chose to move to United ahead of the champions, Mancini added: ''I don't know if he listened to his heart. He took his decision but three or four months before that we were there. We were very close and we were sure it would be very good for us, but it didn't happen and now we can do nothing about it.''

City's four strikers - Sergio Aguero, Carlos Tevez, Mario Balotelli and Edin Dzeko - have contributed 23 of City's 38 goals in the first 20 games this season, 12 fewer than United from the same number.

Chelsea and Arsenal have also scored more than Mancini's side yet the Italian declared himself satisfied with his forwards, despite missing out on van Persie.

''I am happy with my strikers because last season they scored more than anyone else in the Premier League,'' Mancini said.

''But when you can improve your team with other top players it is important to do it.''

If Mancini is feeling under pressure after falling seven points behind United then he was not showing it as he publicly wished Sir Alex Ferguson a happy 71st birthday. ''Happy birthday, congratulations because I think now they deserve to stay on the top,'' he said.

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