Unseeded Australian John Millman has charged into the US Open fourth round in a major career breakthrough.

Millman wore down Kazakhstan’s Mikhail Kukushkin 6-4 4-6 6-1 6-3 to venture to the last 16 of a grand slam for the first time.

The 29-year-old’s reward – in addition to a guaranteed $370,000 pay day – is a clash with either 20-times major winner Roger Federer or Davis Cup teammate Nick Kyrgios on Monday for a place in the quarter-finals.