RIO DE JANEIRO - The International Olympic Committee (IOC) has sounded a warning to Rio 2016 officials about delays to key infrastructure projects.

The IOC's coordination commission completed a three-day inspection of the city on Wednesday, saying the next 12 months would be crucial to the Games' preparations.

"Many projects will have to be delivered simultaneously," commission president Nawal El Moutawakel said during a press conference.

"Despite this large amount of work still to be done, we remain confident, but we must all stay vigilant and continue to work hard so that the timelines are respected."

The visit was the commission's fourth since Rio won the right to host the Games in October 2009.

On the agenda were meetings with government leaders and local organizers along with tours of venues such as the revamped Maracana Stadium, which will stage the opening and closing ceremonies.

"We will leave Rio satisfied by what we have seen and heard," El Moutawakel said. "Time is of the essence but we have confidence that Rio and Brazil will deliver.

Despite the IOC's optimism, several important issues remain unresolved.

Local organizers are yet to reveal an official budget for the Games while venues for rugby, golf, basketball, diving and dancing are still undecided.