The Brasilia venue was initially scheduled to be opened on Sunday by president Dilma Rousseff, but rain has prevented the contractors to lay the pitch in time, prompting the 2014 World Cup organization committee to delay the opening.
"Without the grass it would be like opening a theater with no stage," Brasilia's World Cup secretary Claudio Monteiro was quoted as saying by Reuters.
The Mane Garrincha will not be opened when the finalists of the city's local championship meet next month, which will be the first of two test events required by FIFA.
The second test is expected to be held in a sold out stadium of 72,000 on May 26 when Santos face Flamengo in the first match of the Brazilian top flight.
Only four out of the six stadiums to be used for the Confederations Cup have been opened so far, only two months before the tournament, as the Maracana is still being worked on, too.