Chiasso, Switzerland, 18 April 2013 | AAP

Sam Stosur remains under an injury cloud just two days out from Australia’s Fed Cup World Group Play-off tie in Switzerland.

The Australian spearhead is training with teammates in Chiasso but she’s still recovering from a troublesome calf injury that forced her out of the WTA event in Charleston a fortnight ago.

The French Open contender is confident she’ll be fit for the tie on clay, starting on Saturday, but there are no guarantees.

“Everything is going well but it’s kind of just a race against time kind of thing,” Stosur told AAP on Wednesday.

“I’m still in the rehab kind of phase but I’m out on court practising and things are going well. I’m planning on being fine at the moment and if anything changes we go from there, but as of now I’m definitely planning on playing.”

Stosur first suffered the injury at Indian Wells last month and the lingering problem has raised concerns over her build-up to the French Open, starting on 26 May.

The 29-year-old does not want to jeopardise her claycourt season but is also desperate to help her nation’s cause in the southern Swiss city.

Australia are looking to avoid slipping back into World Group II after working so hard to reach the top tier last year with wins over Switzerland and Germany.

The Alicia Molik-captained team was beaten 4-0 by the Czech Republic in the World Group first round in February.

If world No.9 Stosur is ruled out it would leave Casey Dellacqua (world No.132), Ashleigh Barty (195) and Jarmila Gajdosova (197) facing a mighty task to ensure a spot in the top eight next year.

Switzerland are led by top 60 players Romina Oprandi (52) and Stefanie Voegele (56).