Tokyo governor Shintaro Ishihara on Thursday said he was confident his city's bid to stage the 2020 Summer Olympics would be successful, despite an Asian city being nominated to host the Winter Games.

The decision to hand the South Korean city of Pyeongchang the 2018 Winter Olympics "has nothing to do with us," Ishihara told NTV network.

"There are things we must do. We will do this even if we have to do this twice, three times, four times. We will (campaign) as a national effort," he said.

But doubts have been raised over Tokyo's chances of winning the 2020 Olympics following Pyeongchang's victory, according to Japanese media reports.

Japanese Olympic Committee President Tsunekazu Takeda suggested that Tokyo -- which hosted its first Olympics in 1964 -- may have to delay its bid.

"We should go ahead with our bid if an Asian city still has good chances for 2020, two years after the Winter Olympics in Pyeongchang," he said in Durban, South Africa, according to Kyodo News.

"But we may not if we can't picture ourselves winning after thorough examinations," he said, suggesting that Tokyo might bid for the 2024 Games instead.

Tokyo, Madrid and Chicago lost out to Rio de Janeiro in the race to host the 2016 Summer Olympics.