Attahiru Jega told a meeting in the capital city Abuja that his Independent National Electoral Commission (INEC) had done "everything humanly possible" for a free, fair, credible and peaceful vote on March 28.
INEC has come under close scrutiny since last month when Jega was forced to postpone the February 14 general election on the grounds that troops could not provide adequate security on polling day.
Nigerian soldiers, backed by troops from Cameroon, Chad and Niger, are currently involved in a major offensive against Boko Haram, which has seized swathes of territory in Nigeria's northeast.
Despite a series of claimed military successes, security fears remain over the safety of polling stations after an increase in bomb and suicide attacks in recent weeks.
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Jega maintained that the election would be peaceful, despite the insurgency and election-linked violence, and said the six-week delay had given his organisation more time to prepare.
A week before February 14, INEC said that two-thirds (66.5 per cent) of the 68.8 million registered voters had collected their ID cards, prompting claims that it was unprepared.
But he added: "The level of collection... Nationwide is about 56 million out of these 68.8 million (81 per cent).
"So, there are millions of cards out there that... People have not gone out and collected."
President Goodluck Jonathan's ruling party has raised concerns about the use of electronic card readers, claiming it is untested technology, as well as the rate of distribution of cards.
But Jega said the card readers, which scan fingerprints and record personal data against the electoral roll, will work and reduce the possibility of the persistent problem of fraud.