"I am ready, and if I am healthy, God willing, I will be with you until 2019, until 2021," said the 54-year-old.
In 2007 Chavez lost a referendum on changing the constitution to abolish term limits.
He is not allowed to put the bill forward again. However, others can propose it for him - but the change must be approved by a nationwide referendum.
"Last year, when we lost the referendum, I said I should accept the majority's decision,'' Chavez said at the rally.
But now, he added, "I say you were right: Chavez will not go.''
The proposal will be divisive, with Chavez's opponents claiming that he wants to be president for life.
Gerardo Blyde, the opposition leader, said that the revived idea would not be popular.
"It's going to be an uphill battle for him,'' said Blyde, who suggested that the president is losing support due to high levels of inflation, crime and collapsing infrastructure.
Chavez has been president for almost 10 years over two terms. His current term - which is legally his last - ends in 2013.