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The world No.1 entered the clash with Zhang, ranked No.42 in the world, on a 35-match winning streak against players outside the ATP's top 20.

There was to be no upset in North Rhine-Westphalia, although Zhang pushed him close in a match that featured just one break, Sinner doing the honours in the ninth game of the opening set.

Zhang failed to convert the lone break point generated in the second set as both players served confidently, the Chinese No.1 winning 79 per cent of first-serve points to Sinner's 75 per cent.

However, the Italian's quality shone through in the tie-break, the Australian Open champion converting his third match point to advance. 

Sinner will have a chance to capture his first title on grass on Monday (AEST), which would represent the best possible preparation for a tilt at Wimbledon.

He is just the third player to reach the Halle Open final while top of the world rankings, after Roger Federer (in 2004, 2005, 2006, 2008 and 2018) and Daniil Medvedev (2022).

Hurkacz will be his final opponent after he pulled off an upset of Zverev earlier in the day, the No.5 seed from Poland producing a big-serving display in a 7-6 (7-2) 6-2 win.

Sinner and Hurkacz played doubles together earlier this week, saving two match points in a thrilling win over Nathaniel Lammons and Jackson Withrow before going out to French duo Sadio Doumbia and Fabien Reboul the next day.