City will end 2013 just a point off the top of the Barclays Premier League having clawed back five points on leaders Arsenal over the course of the last month.
Pellegrini had said he wanted to be top, or at least within three points of it, by January.
With that aim completed, and progress also made in the Champions League and Capital One Cup, he is now looking forward to a strong push over the remainder of the campaign.
The Chilean, whose side are back in action at Swansea on New Year's Day, said: "I think it was a fantastic month for us.
"We played nine games in December, we won eight and drew just one.
"In the Premier League, from the last seven we won six.
"It was very important for us to recover points. Arsenal were six points ahead of us so it is very important to finish the year in the position we wanted to be.
"To recover six points in a month is not easy.
"We continue in Capital One and Champions League so I think the first six months of the year were very good for us. Now in the second half we try to win."
Despite their superb form, City have found the going tough in their past two games.
City did well to hang on for a 2-1 win as Liverpool made life difficult on Boxing Day and two days later they could only manage a 1-0 victory over battling Crystal Palace.
Pellegrini expects more of the same at the Liberty Stadium even though the Swans have not won in five Premier League games and City overcame the Welsh side 3-0 a month ago.
The 60-year-old said: "Every team in the Premier League can cause problems to our team and to all other teams. That is why it is so close, this Premier League.
"I repeat what I have said, six or seven teams will be fighting for the Premier League until the end.
"We will continue exactly the same as in the first half.
"Within four or five points, you have five teams and the second half will be exactly the same.
"Swansea play very well at home and away. We will need to be very strong in all senses, defending and attacking, if we want the three points."
Just six points separate Arsenal at the top from Tottenham in seventh.
Such is the tight nature of the table that Liverpool, who led on Christmas Day, have slipped to fifth in the space of two games.
It could be the closest title race for years, something Pellegrini had suspected might happen.
He said: "It is not a surprise for me. I have lived in Europe for the last 10 years, in Spain, and I always saw the Premier League so I knew there were strong teams.
"The budget of the teams is closer than in Spain, so that is why you have six or seven important teams. All the other teams can't win the league but they are strong teams also."
City will be without playmaker David Silva through suspension while top scorer Sergio Aguero, fellow striker Stevan Jovetic and defenders Martin Demichelis and Micah Richards are still injured.
Right-back Pablo Zabaleta, recently recovered from a hamstring injury, was rested against Palace but will return.
Goalkeeper Joe Hart will play despite needing five stitches in a wound under his left eye suffered in the Palace match.
Pellegrini was frustrated by what he perceived as a defensive approach from Palace in that game but he accepts his team must learn to deal with such tactics.
He said: "I don't know what other teams will do in the future here at the Etihad.
"Crystal Palace played the game they thought was the best for them.
"We have to try to resolve the problem, although it is difficult when you are not fresh.
"We played 44 hours after a very tough game against Liverpool.
"What will happen in the future, I don't know, but it is our problem to resolve."