Manchester United returned to the top of the table on goal difference with a 2-0 win over Portsmouth at Old Trafford last night - their 10th in 12 league games since drawing with the Gunners in November.

Chelsea, though, are still only four points behind after they beat Reading 1-0 to make it five straight wins, and Avram Grant's side are undefeated after losing at Arsenal on December 16.

Following another loss for Liverpool, to a last-gasp penalty, at West Ham, it now seems very much a three-way battle for the title.

Gallas, who left Stamford Bridge in August 2006, knows the challenge of his old team-mates cannot be taken lightly.

"Everybody forgets Chelsea - but I do not, because I know how they play," the Arsenal skipper said,

"They can come back very quickly and can put the pressure on Manchester United and Arsenal.

"But we have to also put some pressure back on them, because at the moment they are wining every game.

"We have to be careful because they are a danger."

The 30-year-old added on Arsenal TV Online: "I think it is really exciting to have some pressure in every game and try to win every time.

"We will look to put pressure on both Man U and Chelsea."

Arsenal's young side, lead by the experienced head of Gallas, have certainly performed beyond expectations this season - even if manager Arsene Wenger always felt they had the potential to deliver, even without talisman Thierry Henry.

The 19 goals of Togo frontman Emmanuel Adebayor have certainly helped, as the in-form African took his tally to nine in seven games.

Gallas though knows the rest of the side must continue to chip in and not put too much expectation on the broad shoulders of the 6ft 4ins 23-year-old.

"Manu is very important for the team. At the moment, he is feeling good and playing well," said Gallas.

"We are all happy for him and he wants to score in every game. It is important for every striker to have that ambition, to win something this year with Arsenal.

"He has to continue now, because for me he can be the big striker.

"But we have to help him as well.

"I do not want everything to be on his shoulders, that would be too much for him.

"Against Newcastle, [Mathieu] Flamini and Cesc [Fabregas] also scored. It is important to show everybody that not only the strikers can score, but that the midfielders can too."

Arsenal travel to Manchester City for Saturday's televised lunchtime kick-off.

Sven-Goran Eriksson's men have dropped from their early season pace to lie sixth following a 1-1 draw at bottom club Derby last night which makes it just one league win in seven.

Nevertheless, Gallas knows Arsenal cannot afford to be anything other than fully focused at Eastlands.

"Every game is important for us, because everybody wants to beat us," he said.

"On Saturday, we will play against Man City, which will not be easy.

"We have to win, though, because we have the ambition [to win the league] and have to play like we can do at home.

"Sometimes that is not easy because we are away and do not play the quick football.

"No team plays away like they do at home, but maybe we have to change that."

Wenger may have to make do without winger Tomas Rosicky again this weekend, as the Czech international recovers from a hamstring problem.

Although Dutch striker Robin van Persie has returned to training, he will not be rushed back into action from a thigh injury.

There has, so far, been little activity during this month's transfer window at Emirates Stadium, and there does not appear to be much movement likely during the final hours.

Theo Walcott has rejected claims he would benefit from a loan move, and veteran keeper Jens Lehmann turned down the chance to join Borussia Dortmund, while youngster Luke Freeman has arrived from Gillingham.

Midfielder Abou Diaby has now agreed a new long-term deal, and Flamini - out of contract in the summer - could well follow.