We can ask the contractors to push it, but we have no idea if it's doable
Japan are unable to guarantee they will meet an International Olympic Committee deadline to complete work on the new National Stadium in time for the 2020 Games.
IOC vice president John Coates, on a visit to Tokyo on Tuesday, asked Japan to deliver the stadium by January 2020 ahead of their hosting of the Games which are scheduled to take place from July 24-Aug. 9.
Japan's Olympic minister Toshiaki Endo said the deadline, set in order that the venue could host necessary test events prior to the Games, would be tough to meet.
"It was going to be April on a very tight schedule," Endo was quoted as saying by Kyodo News of the planned completion date.
"We can ask the contractors to push it, but we have no idea if it's doable."
Japan scrapped its original plan for the new National stadium last month in the face of widespread outrage after costs ballooned to $2.1 billion, nearly twice original estimates -- an unusual move for an Olympic host city this late in the process.
Earlier this month, Japan approved guidelines for its new Olympic stadium, vowing to build an athlete-friendly stadium as cheaply as possible.
Kyodo said Australian Coates, head of the Coordination Commission for the Tokyo Olympics, had stressed the new stadium would not require a 80,000 seating capacity as with the original futuristic designed venue by U.K.-based Zaha Hadid Architects.
The stadium issues are not the only problems to have hit preparations for the Tokyo's second Olympics.
Organisers have rolled back on promises to have most venues within eight kilometres of the Olympic Village, while the Olympic logo has become the focus of plagiarism accusations which Japan and its designer deny.