Brisbane, QLD, 8 January 2020 | Murray Wenzel (AAP)

Sam Stosur’s run at the Brisbane International has been ended by Madison Keys, one of three Americans to win in the second round on Wednesday.

Stosur’s bright start to the summer was halted by the power of Keys in a 7-5 6-3 second round loss.

Local hope Stosur had upset former world No.1 Angelique Kerber to progress beyond the first round for just the second time in seven years on Monday.

And the veteran started well against the eighth seed and 2017 US Open finalist by grabbing an early break to lead 3-1.

But the American responded with a break of her own, and applied the pressure again in the 12th game to seal the first set.

Keys broke serve again to begin the second before, behind 10 aces, going on to seal victory in 77 minutes.

Former US Open champion Stosur will continue her Australian Open preparation at the Hobart International.

Australian world No.1 Ash Barty won’t begin her singles campaign until Thursday but is already just one win from the doubles final.

Barty combined with Dutch talent Kiki Bertens to beat second seeds Nicole Melichar and Yifan Xu 6-3 6-2 in less than an hour on Wednesday.

In the semifinals she and Bertens will face another Aussie, Ajla Tomljanovic, and French partner Kiki Mladenovic after that duo beat Karolina Pliskova and Donna Vekic 6-2 6-4 earlier on Wednesday.

Barty will play Jennifer Brady in the second round of the singles on Thursday, while Tomljanovic faces second seed Pliskova.