Sao Paulo's Itaquerao World Cup stadium will be incomplete when it officially opens April 15, according to media reports.
The Brazilian newspaper Folha de S. Paulo said the venue's roof, corporate boxes and big screens will not be ready on time, reported Xinhua.
The new stadium's first official match will be between Corinthians and Flamengo April 27.
A spokesperson for Brazilian top-flight club Corinthians, who own the stadium, confirmed Tuesday the stadium would not be fully ready, but denied pending work was cause for concern.
Earlier, UEFA chairman and World Cup organizing committee member Michel Platini revealed FIFA was still seeking guarantees about the venue.
"There are question marks over the number of seats. FIFA wants to know exactly how many there will be," Platini said.
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"There are also complementary structures which nobody wants to pay for."
According to Corinthians, the 68,000-capacity venue will comprise about 20,000 temporary seats for the World Cup.
The Itaquerao will stage six World Cup matches, including the opener between Brazil and Croatia June 12.