Serena Williams said Friday that she will not reconsider her decision to retire from tennis, but added: "You never know".

Williams suffered what was almost certainly a career-ending defeat when she was knocked out of the US Open by Australia's Ajla Tomljanovic.

"Will you reconsider?" a tearful Williams was asked on court. "I don't think so, but you never know."

The 23-time Grand Slam title winner, and six-time champion in New York, lost her third round clash 7-5, 6-7 (4/7), 6-1.