The Japanese government on Friday approved plans for the building of the main stadium for the Tokyo 2020 Olympics at a cost of almost US$1.5 billion.

Construction of Tokyo's new national stadium is scheduled to begin in December, more than a year after the original blueprints were torn up on the orders of Prime Minister Shinzo Abe amid public anger over skyrocketing costs, according to officials.

The showcase Olympic stadium is set to be completed by the end of November 2019, said the Japan Sport Council -- five months behind schedule, the delays already having forced the 2019 Rugby World Cup to switch venues for the final match.

The US$1.47 billion price tag for architect Kengo Kuma's design comes in just under the US$1.55 cap for the contractors, led by construction giant Taisei Corp.

New Tokyo governor Yuriko Koike, who has been eager to further slash costs for Tokyo's second Olympics, promised to keep a close eye on progress with the city's preparations already dogged by controversy.

"Given we are sharing the (financial) burden, I will raise my voice when necessary to ensure the stadium is utilised by the citizens of Tokyo," she told reporters after a meeting at the prime minister's office.

Japanese Olympic officials have come under fire after a series of embarrassing gaffes since beating out Madrid and Istanbul in the bidding race three years ago.

Prime Minster Abe tore up initial plans for the Olympic stadium, designed by the late Iraqi-British architect Zaha Hadid, as costs soared beyond US$2 billion.

Tokyo organisers then had to scrap the original Games logo after accusations of plagiarism from a theatre in Belgium.

Most alarmingly, French prosecutors launched an investigation into $2 million in payments they suspect were made to help Tokyo secure the Olympics.

Japanese Olympic officials have strenuously denied any wrongdoing.

But Koike's Tokyo government recently appointed a group of academics and business leaders to study ways to cut escalating costs and reduce the burden on the city's taxpayers.

The panel warned in a report published on Thursday that the Games could end up costing more than US$30 billion, urging Olympic leaders to ditch plans to build new venues and use existing ones.

Koike agreed to examine proposals to overhaul the swimming, volleyball and kayak facilities, currently estimated at some US$1.5 billion.