The World Cup squads are preparing to fly, the performers for the opening ceremony are in rehearsal, and Fifa officials have finally taken the reins for the run-in to Brazil 2014.

But with less than three weeks until the competition kicks off on 12 June, the venue for the first match has still to complete trials that should have been finished months ago.

The delays at São Paulo’s Itaquerao stadium – where the roof had to be scaled back at the last minute – are among several remaining hiccups in the preparations for a tournament that has been dogged by the deaths of construction workers, protests, strikes and overspending.

Government officials also warned this week of potential problems with mobile phone coverage during matches, while Fifa executives – who have moved to take control of the stadiums in the past few days – said there was still outstanding work to complete to ensure the event was a success.

After a final inspection of the 12 venues, the Fifa secretary general, Jerome Valcke, gave the tournament the green light, but admitted preparations were not yet complete. “The Fifa World Cup has already arrived in Brazil. And the whole world is watching in anticipation,” he wrote on Twitter. “We have busy days ahead of us with still a lot to be done.”