Aug 9 (Reuters) - World number ⁠one Aryna Sabalenka suffered a setback in her U.S. Open ⁠build-up after she was beaten 7-6(3) 4-6 6-4 by Russia's ‌Ekaterina Alexandrova in the fourth round of the Canadian Open in Toronto on Saturday.

The 16th-seeded Alexandrova fought a hard battle lasting nearly two and a half hours to ​secure her quarter-final berth.

Sabalenka, a four-time Grand ⁠Slam champion and reigning U.S. ⁠Open winner, recovered from a set down to force a decider but ⁠was ‌unable to halt Alexandrova's aggressive shot-making in the final set.

The Belarusian broke early in the opening set before Alexandrova rallied ⁠to force a tiebreak, which the Russian won ​to move ahead.

Sabalenka responded ‌by seizing control of the second set with a break ⁠for a ​4-3 lead before serving out to level the match.

Alexandrova held her nerve in the decider as Sabalenka's error count rose. Serving to stay in the ⁠match at 4-5, the top seed saved ​two match points, but a double fault on the third handed victory to the Russian.

"I just tried to play every single point as if it ⁠was the last one because with her, you don't (get) a lot of chances during the match," Alexandrova said in her on-court interview.

"Honestly, I was trying not to think about the score or anything. Just ​hit the ball, and that's it.

"I'm super happy ⁠that I could win because after the second set, I thought (the chance) ​was already past me."

Alexandrova will face Ukraine's ‌Elina Svitolina, who defeated American eighth ​seed Amanda Anisimova 6-2 6-4, for a place in the semi-finals.

(Reporting by Suramya Kaushik in Bengaluru; Editing by Sonali Paul)