Victoria Azarenka applauds Ana Ivanovic display

World number two Victoria Azarenka has paid tribute to Ana Ivanovic for her performance during their fourth-round clash at the US Open.

The Belarusian advanced into the last eight at Flushing Meadows after a 6-4 3-6 4-6 victory over the Serbian on Tuesday.

Azarenka, who squandered three match points before securing the win, was full of praise for her opponent after a thrilling encounter.

"Ana just came out firing, she played amazing tennis in the first set, ripping winners and serving great," Azarenka said in a courtside interview. "I really had to wake up in the second set.

"In the second set, I felt I was determined, more focused and taking more opportunities.

"The match points were pretty bad. I really didn't go for my shots, I kept waiting for mistakes and something to happen."

Azarenka will meet Daniela Hantuchova in the quarter-finals.