Geopolitical tensions simmered at the U.S. Open on Thursday as Ukrainian Marta Kostyuk refused the customary handshake at the net after losing to Belarusian Victoria Azarenka 6-2, 6-3 in the second round.

The pair exchanged a quick racket tap after Kostyuk hit the ball into the net on the third match point to send Azarenka, a three-time finalist, into the third round.

“Well, I wasn’t surprised,” Azarenka said. “I don’t believe that making a big deal out of it is important. I always shake hands with my opponents,” she continued, adding that Ukrainian Dayana Yastremska had done the same after a match in Washington last month.