Football's governing body said it had reached a settlement with stadium owners Corinthians the day after the two parties were involved in a public disagreement.
Corinthians president Andres Sanchez said there had been some misunderstanding between the two sides, but promised to have the stadium completed on the originally agreed date of December 31.
"This was an excellent meeting. There was some misunderstanding but Sao Paulo and Corinthians are aware of their responsibilities," Sanchez said, according to a FIFA statement.
"I have always been sure that we would host the opening game of the 2014 World Cup and now I am even more. The schedule agreed with FIFA will be respected."
FIFA has demanded that all Brazil's World Cup stadiums are finished by the December 31, repeatedly saying there would be no exceptions.
Doubts arose last week when the chief engineer at the Itaquerao stadium said that, although the main 48,000 capacity part of the stadium would be ready on time, the additional 20,000 temporary seats which will be added for the World Cup would not.
FIFA Secretary General Jerome Valcke said on Tuesday delays would not be tolerated and that it could change the stadiums until August 1.
Corinthians then defied FIFA, saying it had already been agreed that the deadline for the Itaquerao would be extended until February and that football's governing body was free to move matches elsewhere if it wanted.
Valcke, who last year angered Brazilians by saying the country needed a "kick up the backside" to get preparations moving, agreed the two sides had made up at Wednesday's meeting.
"We are very satisfied with the meeting and with the fact that we could talk face to face. Sao Paulo will be an example for other cities to deliver the stadium in time, by December 31," said Valcke.
"The discussion with Corinthians was very fruitful since we understand we both want the same goal, to have the stadium ready," he added. "It is also a special project because of the legacy it leaves for the east zone of Sao Paulo."
