Japan's Naomi Osaka is through to the final of the grass court tourmanent at Bad Homburg

Bad Homburg (Germany) (AFP) - Four-time Grand Slam winner Naomi Osaka is into the first grass court final of her career after blasting past China’s Wang Xinyu at Bad Homburg on Friday.

The Japanese sixth seed Osaka won 6-3, 6-3 in sweltering conditions at the key Wimbledon preparation tournament and will face Czech fourth seed Karolina Muchova in Saturday’s final.

With the mercury topping out at 38 degrees Celsius (100.4 Fahrenheit), the semi-final between Muchova and Romanian Elena-Gabriela Ruse was suspended for more than an hour and a half due to extreme heat.

The match resumed and Muchova won 6-4, 6-4 in one hour and 40 minutes, not including the delay.

Tournament organisers also brought forward Saturday’s final to 11am local time, amid predictions of 41 degrees later in the day.

After her match, Osaka said she was thrilled to reach a first career grass court final but had her eyes on the big prize.

“I’m also really happy, but there’s one more match to be played and we’re going to focus on that,” Osaka said.

Osaka said her daughter, who will turn three during Wimbledon next week, was already waiting in London but was not yet aware of her mother’s true occupation or status in the game.

“I don’t know if she knows I’m successful, I think she just knows I play tennis,” said the 28-year-old.

“Sometimes when we’re at home and I pick up my tennis bag, she’ll ask ‘Oh, are you going to play tennis?’

“I don’t know if she really likes it, but I think she knows what I do, but she probably doesn’t know how good I am at it.”

Osaka blasted six aces and broke her opponent once to take the first set comfortably.

Early in the second, Xinyu answered an Osaka break with a break of her own but the Japanese player quickly wrestled back control of the match.

Osaka broke Xinyu again and took the match in one hour and 10 minutes to continue her strong grass court form just days out from Wimbledon, where she has been handed the 14th seed.

Osaka won two titles apiece on the hard courts of the Australian and US Opens, but has struggled on grass, never making it past the third round at Wimbledon.