Mr Deby took power in a coup in 1990 and later introduced elections.
A referendum in 2005 scrapped a clause restricting presidents to two terms, but Mr Deby said that if he gets re-elected he will reinstate it.
In the last year, Burundi, Rwanda and Congo-Brazzaville have all changed their constitutions to allow their presidents to run for office again.
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Mr Deby said on Tuesday that reinstating term limits would provide "vitality" to the democracy.
"We must limit terms, we must not concentrate on a system in which a change in power becomes difficult," he told the ruling party.
"In 2005 the constitutional reform was conducted in a context where the life of the nation was in danger," he added.
Africa's longest-serving leaders:
The arrogance of power
The Mobutu and Gaddafi effect

A sobbing Minami Minegishi apologised to her fans and said she did not want to leave the band AKB48, in the video seen by millions on YouTube.
The production company behind AKB48 said Minegishi, 20, had failed to abide by its cardinal rule - no dating.
But fans have defended her, saying she is entitled to a normal life.
Head shaving is a traditional form of showing contrition in Japan.
Minegishi's apology came hours after a tabloid newspaper published photographs of her leaving the apartment of her boyfriend, Alan Shirahama, a dancer in a boy band.
In the video posted on AKB48's official website, she said she had made the decision to shave off her long hair to show contrition for her "thoughtless and immature" actions.
"I don't believe just doing this means I can be forgiven for what I did, but the first thing I thought was that I don't want to quit AKB48," she said.
At times sobbing and bowing her head during the nearly four-minute-long video, she also said: "If it is possible, I wish from the bottom of my heart to stay in the band. Everything I did is entirely my fault. I am so sorry."
Minegishi was one of the original members of AKB48 when it was launched by producer Yasushi Akimoto in 2005. The band is made up of some 90 girls - whose ages range from mid teens to early 20s - who, in teams, appear daily in their own theatre and regularly on television, in adverts, and in magazines.
They portray an image of cuteness known as "kawaii", and have become a huge phenomenon both in Japan and increasingly in other Asian countries, correspondents say.
The condition for being part of such a successful act is that the girls must not date boys, so as not to shatter their fans' illusions.
AKB48's management office said Minegishi had been demoted to a trainee team as punishment "for causing a nuisance to the fans".
But author and critic Hiroki Azuma said it was "disgusting" that the star felt she should resort to a traditional act of contrition when the only rules she had broken were those of her band's.
Some fans and commentators say Minegishi went too far with her public apology, and that it was unnecessary.
"What's the point of this public execution show? It's like something from the war or a totalitarian state," one fan said on Twitter.
Chad's President Idriss Deby has announced he will run for a fifth term in April's elections.
[NEXT_CONCEPT]
A Japanese pop star has shaved her head and offered a filmed apology after breaking her management firm's rules by spending a night with her boyfriend.