Tomic battled back doggedly from a set down to defeat defending champion Jarkko Nieminen 6-7 (8-6), 6-4, 6-2 to move to within two victories of a long- awaited maiden tour title.

The 20-year-old will take on either Italian third seed Andreas Seppi or Spanish eighth seed Marcel Granollers today for a place in tomorrow's twilight final at Olympic Park.

Tomic's only other tour semi-final ended in defeat against Andy Murray last January in Brisbane.

Despite being below his best against the crafty Nieminen, Tomic will be a warm favourite no matter who he plays after extending his unbeaten summer streak to six straight wins.

The 2011 Wimbledon quarter-finalist now boasts 17 victories from his past 19 matches in Australia, an imposing record ahead of his home grand slam beginning in Melbourne on Monday.

But his latest triumph was hard-earned.

"I was happy with myself to stay in there," Tomic said.

"Early in that second set, I felt like he was going for shots and was relaxing and for me to stay in there until that three-all point was really big.

"After I won that second set, I freed up and played better tennis."

Tomic fought hard to recover from 5-2 down in the opening set, only to blow his own 5-2 advantage in the tiebreaker.

He had two set points at 6-4 and wasted his best chance on his own service when he overcooked a routine forehand.

Heartened by the reprieve, Nieminen continued to attack and was rewarded with the first set.

"I was very concerned after that first set," Tomic said.

Living on the edge, Tomic grabbed the sole break of the second set late when Nieminen faltered trying to stay in it at 4-5 down.

The Finn's poor service game ended quickly when he put two balls in the net to allow Tomic back on level terms.

Despite his experience, Nieminen has converted only two of his 12 finals into titles and it showed as the left-hander capitulated in the deciding set.

He surrendered his second service game of the set and, rather embarrassingly, the one-time world No.13 shanked his second serve on match point.

Earlier, big-serving South African Kevin Anderson and Frenchman Julien Benneteau, last year's runner-up to Nieminen, booked their places in today's semi-finals.

Anderson downed Uzbek Denis Istomin 6-4, 6-3, while Benneteau eliminated American qualifier Ryan Harrison 6-4, 6-2.

Benneteau, a journeyman who has spent 13 years on tour without claiming a singles title, had a double win yesterday.

With world No.13 Isner withdrawing from the Open with a knee injury, the 35th- ranked Benneteau was elevated to the 32nd and last seeding for today's draw in Melbourne.