The guarantee came eight days after two workers died when a crane collapsed on part of the venue's facade, reports Xinhua.
FIFA president Sepp Blatter told the media ahead of Friday's 2014 World Cup draw that there was no plan B for the Sao Paulo venue.
"We have received information that it will be ready on April 14 or 15," Blatter said.
"We believe it is a question of trust. It will be done."
The Itaquerao stadium will host six World Cup matches, including the tournament opener June 12.
Earlier, Brazil's Sports Minister Aldo Rebelo admitted that five other Word Cup venues -- in Curitiba, Porto Alegre, Cuiaba, Manaus and Natal -- would also miss FIFA's original December 31 deadline.
All except Curitiba are expected to be ready by January.
The World Cup will be held in 12 Brazilian cities from June 12 - July 13.
--IANS (Posted on 06-12-2013)