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It was the second time in as many days that Fritz was pushed all the way and had to come from behind, but he prevailed 5-7 7-5 7-5 in just fewer than two and a half hours.

The American attempted to pile the pressure on early, forcing five break points in the fourth game, but Bellucci got an important hold to level the score at 2-2.

That then set him on his way to getting the all-important break in the penultimate game of the set, but it took him three set points to take the lead.

There was little to split the pair again in the second, and Fritz almost gave himself a mountain to climb, but held off a break point to go 6-5 up before forcing a decider.

It was not until the final game of the third set that the No.2 seed got another break as he converted his second match point to reach the final four.

"I was happy to get through another one like that," Fritz said.

"It was a pretty tough match, and I am really being tested in the first two matches here. I am super happy to get through.

"One of the most important parts of playing on grass is winning those big points and getting through those close matches, as there will be a lot of them on grass."

Fritz will face Alexander Bublik for a place in the final after the No.3 seed defeated Giovanni Mpetshi Perricard 7-6 (7-5) 7-6 (7-3), with neither player facing a break point in the match.

Jiri Lehecka also joins them in the semi-finals after a 6-4 7-6 (7-4) victory over Frances Tiafoe, but he will have to wait to find out his opponent.

Ben Shelton and Sho Shimabukuro's quarter-final was suspended because of bad light, with the Japanese qualifier leading 6-4 after the first set.

Shelton had been looking to pull off double-duty after he beat Marcos Giron 6-7 (4-7) 6-4 7-6 (7-5) earlier in the day to reach the last eight, after his match on Friday (AEST) was also interrupted by the weather.