The stadium in Brazil's western city of Cuiaba had been earmarked to be ready this weekend, five months after FIFA's original deadline, reported Xinhua.
But FIFA secretary general Jerome Valcke said Wednesday the date has been extended by eight days to allow the final 5,000 seats to be installed.
"There is no major issue," Valcke said during a press conference after inspecting the stadium.
"It's just work to be finished and just to make sure that we can run some test events and we can be ready for the time we will receive the stadium from the city.
"I'm fine, I'm happy with Cuiaba and as long as we keep this date of the 5th of May for all the seats to be installed and some additional work to be done."
Arena Pantanal is one of three stadiums yet to be ready for the June 12-July 13 event.
It is scheduled to host four World Cup group matches: Chile-Australia, Russia-Korea, Nigeria-Bosnia and Colombia-Japan.