Pyeongchang (South Korea) (AFP) - American teenage sensation Chloe Kim romped to Olympic snowboarding gold in the women's halfpipe Tuesday before bursting into tears as the enormity of her achievement sunk in.

The 17-year-old, who has melted the hearts of home fans in Pyeongchang thanks to her ever-ready smile and Korean heritage, justified her status as the hot favourite with an eye-popping top score of 98.25.

Kim had been assured of gold before her pulsating final run after China's Liu Jiayu crashed on her last descent.

Pumping her fists after finishing with back-to-back 1080 spins, Kim was serenaded by a pumped-up crowd chanting: "Chloe Kim, Chloe Kim!"

But after wrapping herself in the American flag, Kim was suddenly overcome with emotion and the tears flowed as she celebrated with her Korean parents.

"I'm a little overwhelmed," she said after composing herself. "I don't really know what's happening and I'm actually feeling a little anxious right now.

"There was a lot of pressure," added Kim, who was so good at 13 she might have won gold in Sochi -- but she was too young to compete.

"You wait for four years and it's pretty nerve-wracking. There definitely was a lot of hype but I'm proud of how I was able to handle the pressure today."

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Liu claimed silver with a score of 89.75 points and American Arielle Gold the bronze four points further back.

But neither looked like threatening Kim, who found time to take to Twitter between runs to complain she was having trouble keeping down her breakfast.

- 'Insane feeling' -

"I wanted to go bigger and better on that third run," said the four-time X Games champion. "I messed up on my second run so I'm kind of annoyed but I got redemption on my third.

"Those were obviously tears of joy," Kim joked after the medallists were presented with cuddly toys.

"The mascots are cute but standing on top of that podium was an insane feeling."

Kim also revealed that her number one fan -- her Seoul-based grandmother -- had been in the crowd cheering her on.

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"I actually only found out my grandma was at the bottom before my second run," she said.

"So I thought 'this one's for grams!' I can't wait to go shopping with her."

While his daughter was bewitching the local fans, Kim's father, Jong Jin, was spotted waving a hand-made sign which read: "Go, Chloe!"

Afterwards, the proud father admitted to feeling the pressure of his daughter's quest for Olympic gold.

"It was very stressful because the media kept saying Chloe was going to win," he told AFP.

"But nobody knows. We can control the process but we can't control the result. I never thought about gold. All I ever think about is how dangerous snowboarding is and what if she falls," added the worried dad.

"But grandma of course was very happy. She's very sweet to Chloe and when she goes to church next I'm sure she's going to tell all her friends about Chloe's gold medal."