The cost of venues for the Tokyo 2020 Summer Olympics will have to be carefully watched and managed, but the Japanese capital's preparations are otherwise "outstanding," IOC Vice President John Coates said on Wednesday.

Japan said on Monday that the new National Stadium, the centerpiece for Tokyo's second hosting of the Summer Games, will cost ¥252 billion, nearly twice the original estimate, and will be completed in May 2019, two months later than expected.

"No doubt there will be some issues on the cost of the overlay," Coates told a news conference in Tokyo following an International Olympic Committee visit that included an inspection of new venue sites.