PARIS: Ripping a screaming forehand straight through the tennis textbook, Latvian Jelena Ostapenko blazed into the French Open final with a 7-6(4) 3-6 6-3 win over Swiss Timea Bacsinszky in a battle of the birthday girls on Thursday.

On the day she turned 20 the free-swinging world number 47 launched a fusillade of 50 winners to become the first unseeded player to reach the women's singles final at Roland Garros since Mima Jausovec lost to Chris Evert in 1983.

But seven-times French Open champion Evert, in Paris commentating for broadcaster Eurosport, would not have recognised the high-risk tennis served up by Ostapenko who clearly does not subscribe to the old-school theory of waiting for your opponent to make a mistake.

Mixed in with her scintillating winners, including forehands faster than anything men's world number one Andy Murray has managed here so far, were 45 unforced errors, some of which could have embellished a video nasty.

At times it resembled Russian roulette as Ostapenko threw caution to the wind. But there was nothing lucky about the way she prevailed in the biggest match of her career.

"I didn't think I would be in the final but every match I've played better," Ostapenko, whose dad Jevgenijs was a professional football player, told reporters.

"In the third set I just wanted to stay playing aggressive. "It's a great way to celebrate my birthday."

Sixteen service breaks summed up the frantic nature of the contest. Several times Ostapenko seemed on the verge of youthful tantrum in the hot Court Philippe Chatrier sunshine, especially when the Latvian livewire lost four games in a row to lose the second set -- ending it with a double-fault.

Thirtieth seed Bacsinszky, who needed a bandage applied to her right thigh midway through the first set, looked the more likely winner at that point as she sought to celebrate her 28th birthday by surpassing her semi-final run of 2015.

Logic suggested the steady approach she adopted after losing a topsy-turvy first set in a tiebreak would get the job done for the experienced Swiss, not the white-knuckle rollercoaster tennis Ostapenko was playing.

PIZAZZ

But just when the storm appeared to have blown over Ostapenko, who knocked over former runner-up Sam Stosur and former world number one Caroline Wozniacki en route to the semis, hit another purple patch to roar home from 3-3.

With Bacsinszky serving at 3-5 Ostapenko, coiled like a spring, brought up two match points with an unstoppable backhand return that cleaned the baseline then smote a rasping forehand return winner that left her opponent flat-footed.

Bacsinszky fended off one with a swinging serve but Riga's finest made no mistake on the second, sending a forehand whistling into the corner to become the first Latvian player to reach a grand slam final.

Should she win on Saturday against third seed Simona Halep, she would become only the second unseeded player to win the women's title at the French Open after Britain's Margaret Scriven in 1933.

Amazingly it would be her first professional title of any kind -- emulating the feat of Brazilian great Gustavo Kuerten who also announced himself to the world by coming from nowhere to win at Roland Garros in 1997.

With the women's game in need of a new injection of pizazz in the absence of pregnant 23-times major champion Serena Williams and with Maria Sharapova just starting back from a doping ban, Ostapenko has game and personality to sell tickets.

At the moment, however, all she cares about is hitting the ball hard -- very hard -- and seeing where it gets her.

"I'm really happy, I love to be here," Ostapenko, the youngest woman to reach the French Open final since Ana Ivanovic in 2007, said after former Wimbledon champion Marion Bartoli and the crowd serenaded her with a chorus of "Happy Birthday".