International Olympic Committee chief Jacques Rogge has put London 2012's readiness for the Games on a par with Sydney 2000 and Beijing 2008.
The Belgian visited London's Olympic sites on a day of festivities to mark exactly one year until the opening ceremony.
"You can't compare cities," Rogge told the BBC when asked whether London was the best prepared city.
"Regarding operation readiness, I'd put it on par with Sydney and Beijing."
Rogge was particularly impressed with the Aquatics Centre, describing the £269m arena as "a masterpiece".
"I've seen so many venues in my life but when I came up [it] I had a visual shock - this is unique, state of the art," he said.
Rogge also praised London 2012 organisers for finishing the last of the six main permanent Olympic Park venues 12 months ahead of the opening ceremony.
But he urged the London Organising Committee and its chairman Lord Sebastian Coe to be wary of complacency.
"It's all about the delivery of the Games, not just about the preparations," said Rogge. "I have no worries. I just have a clockwatch and that says to me 27th of July, eight o'clock in the evening, next year, you have to be ready."
The IOC president believes that London 2012's only "major challenge" is to have an efficient transport system in place, although he added that all Olympic hosts cities had been faced with that problem.
However, the issue of the Olympic Lanes is a contentious one.
Designed to ensure athletes, officials and media can move quickly and efficiently between the various venues, the Olympic Lanes will result in some of London's roads closed to the public during Games time.
Transport for London (TfL) admitted the lanes would put greater traffic demands on certain parts of the network during the Olympics but Rogger said they were necessary.
"The Olympic Lanes, let me tell you that it is less than 10% of the London territory that is affected," said Rogge.
"It is very much needed because, if you don't have Olympic Lanes, the athletes will not be able to perform and will not be able to compete on time."