The Rio de Janeiro state body for the protection of historical and artistic buildings (Iphan) granted permission for the demolition of the roofing over the stadium's tribunes and its replacement by a new, larger covering.
FIFA has stipulated all the tribunes at stadiums holding 2014 World Cup matches must be covered, which was not the case at the Maracana, built the previous time Brazil held the finals in 1950.
The existing covering was to be enlarged in the original project to refurbish the 82,000-capacity stadium but the government changed its plans and will demolish it after discovering structural problems.
This decision increases the costs of preparing the Maracana for the World Cup and the Confederations Cup a year earlier to more than one billion reais ($629.3 million) from the original budget of 705 million reais.
Completion of the work on South America's biggest stadium is projected for December 2012.
Blatter, who is on a tour of Central America, said last month he was worried by the slow pace of work on the stadiums, especially in Rio and Sao Paulo.
He said Brazil was behind in comparison with South Africa at the same stage of its preparations for the 2010 finals.
However, speaking in El Salvador, Blatter said FIFA was satisfied with the progress being made in Brazil.
He said FIFA had received a positive progress report from the Brazilian Football Confederation (CBF).
"We have received some very positive reports everywhere, especially in the construction not only of the stadiums but also the airports and hotels in the different regions," Blatter told a news conference in San Salvador.
He said on March 28 he was concerned Brazil would not have stadiums in Rio and Sao Paulo ready for the Confederations Cup in 2013, a year before the World Cup, which acts as a dress rehearsal for the finals.
Blatter, who will also visit Honduras and Guatemala on a trip to canvass for votes as he seeks re-election as FIFA president, said security was entirely a matter for the Brazilian government and not the sport's governing body.
The 75-year-old, in office since 1998, faces a challenge for his seat at the June 1 election from Asian Football Confederation president Mohamed bin Hammam of Qatar.
