Stosur will play either American second seed Serena Williams or Russian seventh seed Svetlana Kuznetsova for a place in the final, in what will be the first Roland Garros semi-final appearance for an Australian woman since Nicole Provis in 1988.

Cirstea, 19, had beaten three seeds, including Serbian world number five Jelena Jankovic, en route to the last eight but a nervous double-fault saw her broken in her first service game.

The big-serving Stosur, ranked 32 in the world, then broke again when Cirstea scooped a crosscourt forehand wide before serving out for the set in 27 minutes.

A more tenacious Cirstea forced Stosur to save four break points in the opening game of the second set, before the Australian broke for a 2-1 lead.

Stosur's advantage stretched to 4-1 when Cirstea sliced a backhand into the tramlines in her next service game, with the Australian surviving a late rally from her opponent before breaking again to close out the match.

Should Stosur make the final, she will be the first Australian woman to do so since Wendy Turnbull in 1979.

The last Aussie women's champion here was Margaret Smith-Court in 1973. -- AFP