"The only one city where they have really to speed up and to work on different contractors and the different agreements they have to sign to be ready on time, which is December 2013, is Manaus," Jerome Valcke, secretary general of football's governing body, told reporters.
Valcke said he was concerned that construction of the 44,000-seat Amazonia Arena was not happening quickly enough. The stadium is less than 50 percent ready, according to official figures.
FIFA's guidelines say the stadiums in the 12 host cities must be ready at least six months in advance because the World Cup fixture draw takes place in December 2013 and competing nations need to plan issues such as their team bases.
"For the World Cup we need the stadium in advance, we need three test events," Valcke said on the eve of the draw for next June's Confederations Cup, a tournament designed as a dress rehearsal.
"You cannot have the stadium six weeks in advance, that is technically impossible.
"There is no plan B, you can always decide to take one stadium off. We did it in Germany for the Confederations Cup and South Africa for the Confederations Cup. It works. To be clear, you need a certain time to deliver a certain work."
Although Valcke did not mention Manaus's accompanying infrastructure projects, they are also causing concern in the Brazilian media.
A recent report from Brazil's Audits Court said a $650 million light railway project would not be ready in time. A proposed new system of rapid bus lanes is also behind scheduled and unlikely to be ready for the June 2014 World Cup, the court said.
