document: 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.
  Africa Live: BBC news updates
  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
summary: Chad's President Idriss Deby has announced he will run for a fifth term in April's elections.