SAINT PETERSBURG, Russia (AFP) - US Open champion Stan Wawrinka and Czech Tomas Berdych both cruised into the Saint Petersburg Open semi-finals on Friday (Sept 23).

Top seed Wawrinka beat Serb Viktor Troicki 7-5, 6-2 to set up a meeting with Spaniard Roberto Bautista Agut for a place in the final.

Third seed Berdych, currently ninth in the race to the London ATP Finals - which features the year's top eight players - also advanced past Italian veteran Paolo Lorenzi 6-4, 6-3.

Wawrinka, the world number three, recorded his sixth win over seventh seed Troicki in as many meetings, breaking in the 12th game for a one-set lead.

Wawrinka, 31, underlined his supremacy on the hardcourt surface in the second with two more breaks to close out in 64 minutes.

Earlier Bautista Agut, 28, rallied from a set down to see off Portuguese eighth-seed Joao Sousa 4-6, 6-1, 6-2.

"He's a great player, a great fighter," said Wawrinka of his next opponent who won the last of his four ATP titles on hardcourt in Sofia last February.

"He likes this kind of surface and I'm looking forward to an interesting match," the Swiss added.

Berdych, who has won 12 ATP titles most recently in Stockholm and Shenzhen last year, took the opening set in 35 minutes with a break in the 10th game, breaking early in the second.

"My game is improving day by day," warned Berdych, who next plays German teenager Alexander Zverev, who whipped home favourite Mikhail Youzhny, the 2004 champion, 6-2, 6-2.

"The match was much harder than the scoreline shows," Zverev, 19, insisted.

"I played really tough matches with Berdych earlier this year. But if I play like I did today I think I've a good chance tomorrow (Saturday)."