Atlanta, GA, USA, 28 July 2017 | AAP/

Australian John Millman has been beaten by Ryan Harrison in a three-set, second-round marathon at the Atlanta Open.

Millman, ranked 174th, battled for two hours and 46 minutes before the fourth-seeded American prevailed 6-7(2) 7-6(4) 7-5.

The Queenslander led by a set and a break, reached match point in the ninth game on Harrison’s serve, and served for the match in the 10th game before the American broke to get the set back on level terms.

The decisive break of Millman’s serve came in the 11th game of the final set; Harrison served out the match in the following game.

Joining Harrison in the quarterfinals is Kyle Edmund after the Briton recorded a come-from-behind victory over German Peter Gojowczyk.

Edmund lost the the first set but recovered to come out on top 2-6 6-4 7-5 in the rain-interrupted match.