Madison Keys remains on course for a maiden Grand Slam title after beating veteran Venus Williams to book a semi-final spot at the Australian Open this morning.

The 19-year-old, who had previously never progressed beyond the third round in a major competition, beat the veteran 6-3 4-6 6-4 in a gruelling encounter that lasted just under two hours.

Nothing could separate the players early on as they boasted three games apiece, before a crucial break of serve - the first of the match - helped Keys move 4-3 ahead.

It was the break that the youngster was looking for and she soon held serve to establish daylight in the scores for the first time en route to a 6-3 first-set victory.

Williams, a nine-time Grand Slam winner, outlined her desire to claim an elusive 10th major title by cruising into a 4-1 lead in the second set, before injury forced Keys into a 10-minute time-out.

Keys emerged from the tunnel with a strap over her left thigh, but she defied her injuries by clawing back to level up at 4-4, although the veteran slowed her momentum to win the next two games and achieve parity.

Williams took a 3-1 lead in the decider, but Keys held serve and broke back to level up at three apiece.

The pair broke each other's service game once more, but Keys then served up an ace to move within one game of the semis, and made the most of three match points to set up a last-four clash with either Serena Williams or Dominika Cibulkova.