China's Feng Shanshan celebrated her 32nd birthday in style by firing a flawless 64 in the second round of the Tokyo Olympics women's golf tournament.

The 7-under score hauled Feng, a bronze medalist at the 2016 Rio Games, back into medal contention on Thursday.

After a disappointing 74 on the first day, she sank seven birdies against no bogeys on another sweltering day at Kasumigaseki Country Club to move up to tied-11th place on a 4-under total of 138.

World No 1 Nelly Korda of the United States tied the Olympic record of 62 to open up a four-shot lead on 13-under in the race for the gold medal.

With three players－India's Aditi Ashok (66) and Danish duo Nanna Koerstz Madsen (64) and Emily Kristine Pedersen (63)－sharing second place on 9-under, Feng knows she has her work cut out to bag the second Olympic medal of her career.

Feng's compatriot, Lin Xiyu, fired a 66, which featured one eagle, six birdies and three bogeys, to share ninth place on 5-under.

A Pacific storm that may bring torrential rain and wind to the area by Saturday's scheduled final round could reduce the competition to 54 holes.

"It was pretty good. I knew I didn't do very well yesterday, so plus they're saying that maybe they're going to shorten the tournament to a 54-hole tournament, so I knew I would have to make something happen," said Feng.

"My ball striking was much better, so I gave myself a lot of birdie chances and I made the most of them. So 7-under I think, yes, I'm still behind, but at least I think it's halfway there."

The 10-time LPGA Tour winner credited her putter for the 10-shot improvement.

"I think my putting yesterday wasn't that bad, it was just misjudged－I misjudged the speed a little bit. The greens are actually a little bit slower than what we were thinking. I just couldn't get the ball there, plus my ball striking, I just didn't give myself too many chances yesterday," added Feng.

"I think at least I went from impossible to now maybe have a small chance (for a medal). I would still have to go low for two more rounds because I know the girls are going to play well, because we've got the best girls from all over the world here. I will give it 100 percent."

With fans not permitted on site at this Olympics, the volunteers at the event made sure they wished Feng a happy birthday before she set off for her second round.

"I think like one of the volunteers actually wrote some words for me and she held the board and was showing me on the course," said Feng.

"And I was like, thank you. I guess the tournament maybe was telling them. I was glad that not everybody came to me and said happy birthday because I don't know if I can still concentrate if that happened."

With Tokyo 2020 likely to be her final Olympic appearance, Feng is determined to earn a medal again for China. "We're not really going for prize money. This time we're representing our countries and we're playing for honor," she said. "That's why everybody is trying so hard."