New York, New York - Karen Khachanov reached a grand slam semi-final for the first time as he ended Nick Kyrgios' US Open run in a five-set, three-and-a-half-hour epic on Tuesday evening.

The 27th-seeded Russian, who had fallen in the quarters at the 2019 French Open and 2021 Wimbledon Championships, prevailed 7-5, 4-6, 7-5, 6-7, (3-7), 6-4 over the Australian 23rd seed to set up a semi-final date with fifth seed Casper Ruud.

The result ended the run of Kyrgios, who had won the most matches on the ATP Tour since losing July's Wimbledon final to Novak Djokovic. Kyrgios had taken out reigning champion and top seed Daniil Medvedev in the fourth round.

The 26-year-old Russian athlete broke Kyrgios' serve in the 12th game of the first set with an exquisite lob, clinching the frame where the Australian's second serve let him down.

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Kyrgios responded to win the second set, despite a medical timeout for treatment on his left leg after exclaiming "I can't walk," breaking the Russian early and hitting 12-5 winners.

Khachanov claimed the third set in similar circumstances to the first, with Kyrgios failing to hold his serve in the 12th game, this time producing unforced errors in the key moments.

The two players traded breaks early in the fourth set, but Kyrgios would force a fifth set after a dominant tie-break where he converted his second set point.

The Russian got an early break in the fifth set, while Kyrgios failed to convert break points in Khachanov's next two service games, and he would not recover.