Serena Williams knows she must be at her tenacious best to join sister Venus in the Australian Open semi-finals, with a confident Johanna Konta determined to crash the party on Wednesday.

The American's unrelenting quest for a record 23rd Grand Slam title to surpass Steffi Graf and return to world number one was tested by Barbora Strycova in round four, and Konta won't be any easier.

The British ninth seed has set herself up as a genuine title contender with an impressive nine-match unbeaten streak after winning this month's Sydney International.

At stake is a semi-final with either comeback queen Mirjana Lucic-Baroni or fifth seed Czech Karolina Pliskova, with Venus Williams and fellow American Coco Vandeweghe contesting the other.

Williams, chasing her seventh Australian title, is aware of the danger posed by Konta.