Roberto Mancini held up his hand at Manchester City's training ground to demonstrate how close he believes his club are to catching Manchester United. "This much," he said, holding two fingers narrowly apart. At the start of the season it was "two yards" but now, he said, he had revised his opinion. "Now it's one. United over City, it's one yard now because in these two months we've worked hard and we've closed the gap."

City, in fact, go into Sunday's derby two points clear of their neighbours at the top of the table and Mancini offered a confident reply when he was asked whether they could maintain that position. "Yeah, yeah, I'm sure," he said.

On the longer term, he did not flinch either when it was put to him that Garry Cook, formerly the chief executive, had talked of a day when City would be the bigger club in Manchester. "I think this as well," he said. "I don't know if it will be possible or in how many years but we will work for this."

For now Mancini still believes Sir Alex Ferguson's team have the edge. "Because United is United," he explained. "It is a team that wins something every year – the Premier League, the Champions League, the FA Cup. When one team continues to win every year they are ahead of the rest."

Mancini continued: "They have one thing we still don't have. I watched their game against Norwich – Norwich had I don't know how many chances. Chelsea was the same.

"I've watched two or three of their games. They played Tottenham – first half a normal game, second half 3-0. It's mentality, psychological. This is what I mean. They are a strong team. Even when they don't play very well they still win."

Ferguson said it would be "a wee bit premature writing off Chelsea" but he admitted that the modern-day City represent United's greatest challenge in the Premier League. "Last season was a turning point because they won the FA Cup, the first time they'd won something for 35 years," he said.

"We all reach points in life and say this is a different life now – look at that couple who won €110m on the lottery – but the important thing is we don't go away. They are where they are at the top of the league but at this club we always accept a challenge."