TOKYO (AFP) - Tokyo is looking to slash the price tag for the 2020 Summer Olympics by US$1.7 billion (S$2.2 billion) through scrapping or scaling back plans to build new facilities amid fears over spiralling costs.

Recent estimates put the bill for the venues, including the construction of 10 new facilities, at 450 billion yen (S$5 billion) - three times the initial estimate - triggering renewed belt-tightening measures and even calls to use existing venues as far away as Osaka.

"We reviewed our facility plans after the expense swelled due to unexpected additional construction works and surging costs of construction in general," Katsura Enyo, senior official at the Tokyo metropolitan government's 2020 Games planning division, said on Thursday.

"We presented the revised plan to the IOC (International Olympic Committee) and I think we gained their understanding. What's important is that we build facilities that Tokyoites still find useful after the Olympics are over."

IOC vice president John Coates has urged Japanese officials to look into the possibility of holding more sports outside Tokyo, which would represent an embarrassing detour from the city's bid plan promising that virtually all events would take place within 8km of the Olympic village.

Tokyo's compact bid had been a key factor in beating Istanbul and Madrid for the rights to host the 2020 Games, but Coates suggested basketball preliminaries could be played in Osaka, 400km west of Tokyo.

"We should make the maximum use of existing facilities, and that overrides the 8km philosophy which we had as part of the bid," he said after a visit to Tokyo. "We suggested to the organising committee that for the preliminaries for basketball, just as for football, they may care to look at cities like Osaka that might have large venues."

The 2020 Games are expected to boost the Japanese economy by an estimated three trillion yen as building and tourism-related stimulus power growth, with about half the bonanza going into Tokyo's coffers.

However, Tokyo Governor Yoichi Masuzoe ordered a review of the building plans due to budget concerns earlier this year, and a new main basketball venue could be ditched in favour of an existing arena 25 kilometres north of the capital, while badminton could also be shunted a similar distance away.

Some preliminary matches for the 2020 football tournament will take place in parts of northeast Japan ravaged by the 2011 tsunami in a bid to boost local economies.

"It's not only about money," insisted Enyo. "It's also about how to keep green areas pristine and making sure facilities are user-friendly.

"We want to be sure we leave a good legacy from the Olympics."