Angelique Kerber won her eighth consecutive match of the new season, coming from 3-1 down in the final set to beat qualifier Camila Giorgi 6-2, 6-3 to reach the Sydney International final on Friday.
Kerber, a former No. 1 and the 2016 Australian Open champion, was 4-0 in winning the Hopman Cup and has added four in a row in Sydney en route to the final.
She will face Ashleigh Barty, who beat fellow Australian Daria Gavrilova 3-6, 6-4, 6-2 in the other semifinal.
In a match that included 11 breaks of serve, Barty needed just one in the third set.
"It's nice getting a bit of confidence going into our biggest tournament for us," Barty said of next week's Australian Open.
Gavrilova's frustration with her serving were evident in the ninth game of the set when, soon after leveling at 4-4, she double-faulted twice and received a code violation for smashing her racket.
In men's semifinals, Russian qualifier Daniil Medvedev booked a spot in the final by upsetting fourth-seeded Fabio Fognini of Italy 2-6, 6-4, 6-1.
Medvedev will next play Australian 18-year-old Alex de Minaur, who defeated Benoit Paire of France 4-6, 6-1, 6-1. The 167th-ranked de Minaur, who will play his first ATP Tour final on Saturday, advanced to the Brisbane International semifinals last week.
Mertens to defend Hobart title against Buzarnescu
Elise Mertens will defend her Hobart International title in the Hobart, Australia, final after eliminating 2015 champion Heather Watson 6-4, 1-6, 6-2 on Friday.
Mertens will play Mihaela Buzarnescu of Romania, who has reached her first WTA final.
Buzarnescu beat fifth-seeded Lesia Tsurenko 6-2, 6-2 in her second career semifinal. She is guaranteed to break into the top 50 rankings for the first time on Monday.
Watson, a qualifier, hadn't dropped a main-draw set until running into second-seeded Mertens. The loss was "frustrating," Watson said. "I made too many unforced errors. Because I'd been playing so well, I expected more of myself."
ASB Classic final set
Former champions Juan Martin del Potro and Roberto Bautista Agut will meet Saturday in the final of the ATP Tour's ASB Classic in Auckland, New Zealand.
Second-seeded del Potro, champion in 2009, beat four-time champion and eight-time semifinalist David Ferrer 6-4, 6-4 in just under two hours Friday while Bautista Agut, the 2016 champion, defeated Robin Haase 6-7 (7), 7-6 (3), 7-6 (5) in a three-hour marathon.