Gallas: Tough decision swapping Arsenal for Tottenham
Gallas became the most high-profile player to cross the north London divide since Sol Campbell yesterday when he signed a one-year contract at Spurs.
"It was not an easy decision but I am here now and I will give my best," France defender Gallas told his new club's official website.
"What is most important to me is to play games and to give everything."
The 33-year-old immediately attempted to win the doubters over by claiming he believes he has joined a club capable of winning the Barclays Premier League this season.
"Finishing fourth last season shows Spurs have improved a lot and I hope this season we are going to finish even higher, maybe even win the Premier League," he added.
"We just have to believe in ourselves. We have got young players with great quality.
"They just have to believe in their capacity to do something and I hope we can achieve this."
Speaking after training with his new team-mates, he said: "The atmosphere is great here.
"I like that and I'm just looking forward to playing as soon as possible and winning some games."
Gallas, who is at least two weeks away from being match ready, added: "I just want to be fit as soon as possible, train with my team-mates and play matches. I want to show everybody I am still here."